Database Users

stuck at htc screen - what to do?

ok, it is just a idea
it looks like many people do have the problem that for some reason their phone stops booting at htc screen...
i´m thinking about writing something like a guide (wip) what are the things you could try to get the phone working again (only basic stuff and links, i´m not a dev) - so if anybody got an idea what i should add pls post it
how to check your emmc chip:
http://forum.xda-developers.com/showpost.php?p=13895268&;postcount=48
if one step works stop and don´t go further...
1. post: stock phone (no root)
2. post: rooted phone
3. post: rooted phone & eng hboot
STOCK PHONE - NO ROOT (bootloader shows: hboot: ??? & S-ON):
1. pull the battery and try it again
2. turn your phone in usb fastboot mode (power & tp) connect it to pc; on pc go to platform tools and type fastboot devices (your device should show up) then type fastboot oem boot
3. wipe cache or do a factory reset (= push power & volume down to enter bootloader; select recovery = a red triangle will appear then push power & volume up to enter recovery menu)
3.a. wipe cache = none of your apps are lost
3.b. factory reset = you will loose your apps & sms & so on... but you won´t loose your sdcard content
reboot
4. use a ruu (it´s .exe to start from windows pc) and try to update (install htc sync):
http://shipped-roms.com/index.php?category=android&model=Vision ...for example
5. if point 3 didn´t work, extract the PC10IMG.zip put it on your sdcard (not in a folder) enter bootloader and start the update (more details will follow)
6. hope for warranty

PHONE ROOTED (bootloader shows: hboot ??? & S-OFF):
1. if you enabled usb debugging before, start adb and type adb devices, if your device shows up type adb reboot bootloader (if it worked next step = 4)
2. pull the battery and try it again
3. turn your phone in usb fastboot mode (power & tp) connect it to pc; on pc go to platform tools and type fastboot devices (your device should show up) then type fastboot oem boot
4. wipe cache or do a factory reset (power & volume down to enter bootloader then select recovery) - reboot
5. wipe again (this time use superwipe: http://forum.xda-developers.com/showthread.php?t=1044992) & wipe through recovery then flash a different rom
6. any suggestions?

PHONE ROOTED & ENG HBOOT (bootloader shows: hboot 0.76.2000 |g2| or 0.84.2000 |desire z| & S-OFF):
1. if you enabled usb debugging before, start adb and type adb devices, if your device shows up type adb reboot bootloader (if it worked next step = 4)
2. pull the battery and try it again
3. turn your phone in usb fastboot mode (power & tp) connect it to pc; on pc go to platform tools and type fastboot devices (your device should show up) then type fastboot oem boot
4. wipe cache or do a factory reset (power & volume down to enter bootloader then select recovery) - reboot
4. wipe again (this time use superwipe: http://forum.xda-developers.com/show....php?t=1044992) & wipe through recovery then flash a different rom
5. if you can´t enter recovery for some reason turn your phone in usb fastboot mode and connect to pc:
5.a. wipe cache & data through fastboot (go to platform tools and type fastboot erase cache and fastboot erase userdata) - reboot
5.b. flash a recovery.img through fastboot (download the image and put it in your platform tools folder; go to platform tools and type fastboot flash recovery recovery.img) then enter recovery and flash whatever you want to...
6. any suggestion?

My DZ is with new mainboard now - there was no other way... I tried all steps for "STOCK PHONE - NO ROOT" without success.

chyles said:
My DZ is with new mainboard now - there was no other way... I tried all steps for "STOCK PHONE - NO ROOT" without success.
Click to expand...
Click to collapse
sure if it is a hw defect nothing will work... i planned to add a way to confirm if it´s a broken emmc chip, but if there is no interest in a thread like this i will stop...

there is really not too much to worry about, if you private message me, I can give you Josh's information here on XDA - he can unbrick pretty much any G2/Desire-Z for $40 and has done 100's of them - he has like almost 500 Thanks on here -
the only thing he can't fix is a fried emmc chip, but thankfully those are relatively rare!
(and if the emmc chip is fried, then HTC will fix it, because that truly is their fault, so no worries!)
(HTC knows of the emmc chip failures, and that is why in this case they are not going to give you a hassle about the warranty, sort of like when an auto company has done a silent recall, so to speak)

ADB
Well when i first rooted and installed cyanogen..it got stuck oon the htc screen..pulled the battery(not safe)... so the next time i flashed a rom and this happened i just connected the phone to pc and used adb to reboot into the bootloader....
Confused with all the links to various places for rooting your Desire Z/ G2 ???? Maybe you could find it a little easier on my blog www.desirez.strawmetal.com ... Hope it helps you..

strawmetal said:
Well when i first rooted and installed cyanogen..it got stuck oon the htc screen..pulled the battery(not safe)... so the next time i flashed a rom and this happened i just connected the phone to pc and used adb to reboot into the bootloader....
Click to expand...
Click to collapse
thx, i´ve changed the op

any feedback on this thread? i don´t know the hboot numbers (normal hboot, not eng hboot) for g2 or dz - does anybody know?

" x " appears on the screen

Malfunction " x " appears on the screen !! help me what is going on

Haha... you'll need more information than that if you want real help.
Based on the limited information though I suspect your phone is stuck in a bootloop. I'd hook it up to the PC via USB and check the logcat. Probably something screwed up.. Maybe time to restore your latest backup.

Did you flash any ROM if so, did you clean your Dalvic+REgular Cache

If you don't have an Recovery:
- Connect your Micro SD on PC
- Download and insert on SD the stock ROM of your Nexus One
- Power ON your Nexus with Volume Down Pressed.
- Autmotically Restore Nexus (You should say Yes xD)
At this time, you decide if you want to be root and install other ROM

you better just list your setup info before doing anything
locked/unlocked bootloader
rooted/unrooted
which recovery are you using
what rom are you running stock/custom
what were you doing when this happened
a couple safe things you can do in meantime is to pull battery and reinsert and power on
if it goes back to X, pull battery and DO NOT power on. Hold down the pwr button and trackball at same time and see if you can get into recovery
the third is hold down trackball/vol-/power at same time while X is on screen and see if you can get to recovery that way
if you can't get to recovery you will need to fastboot new recovery, assuming you are unlocked
once you get into recovery do a nandroid if you are rooted
and copy it to pc as a secondary backup
it is possible you may need to try the passimg method in wiki
http://forum.xda-developers.com/wiki/Nexus_One/Guides_&_Tutorials#Unroot_.2F_Restore_your_Nexus
also to do fastboot commands you need usb debugging selected on phone--hope it is

Hello, i have a similar problem with my n1
the phone starts and just shows the nexus X - (waited for 15 min. nothing happend)
i can go to the bootloader / fastboot menu with PWR + (Vol-) but i can not go to the recovery mode. -> the phone reboots and get stuck at the X
the phone is rooted
blackrose / hboot 7.35.5017
radio 5.12.00.08
recovery was ext4
i had a german ics miui rom installed and tryed to install the latest ics miui us rom after it didn't booted the miui us rom i turned the phone off and tryed a few hours later to turn it on to reflash the german ics miui rom.
1.)
i tryed to install a new recovery image ->
recovery-clockwork-5.0.2.0-passion &
recovery-RA-passion-v2.2.1
(still get stuck at the X if i try to go to recovery mode)
2.)
i tryed this one with the passimg.zip but nothing happens if i put in the sd card :/
(with nothing i mean the green text show that the sd card is checking for PASSDIAG.zip and PASSIMG.zip but dosn't found it)
i also tryed:
3.)
erased boot
flash boot from passimg.zip (PASSIMG_Passion_Google_WWE_2.18.1700.1_FRG83_release_signed)
4.)
erased cache
erased userdata
started again with 1.)
5.)
got frustrated and erased system -.-
any ideas?

study it ,thank you
study it ,thank you

Hmm, sorry if its obvious but i have no idea what it could be or what i have to search to find the solution. Would be nice if you could give me a hint. Of course im not asking for a step by step solution. Thank you.
Send from my awesome SE K800i

not sure why you are flashing boot images
do you have a nandroid--copy your sdcard with the nandroid to pc--all of sdcard
are you flashing thru fastboot in command window
did you read my post above on getting to the fastboot screen--can you do that--the one with the 3 androids
pwr/vol-/trackball same time, may take 20-30 seconds
if you can get there, put your recovery image in your fastboot folder on pc, normally tools--assuming you have sdk installed, your phone must have usb debugging checked--I hope
open a command window and change directory to the tools folder or wherever the fastboot.exe file is. Something like:
cd/
cd/ android/android-sdk-windows/tools for me
then on same line type
fastboot devices (it should show your phone H#)
fastboot erase system
fastboot flash recovery recovery.img (or the exact name of the recovery image, checked by right clicking on the img file in your tools folder and looking under properties)
I would use amonra you listed above and check the md5 if possible
hopefully the recovery will flash
if not you can go to the wiki link i posted above and try passimg metthod from there, use correct one. don't add the .zip. Windows will had it automatically.
a side note, DON"T flash different roms without wiping all including System 3 times before flashing--prevents a lot of problems

rugmankc said:
a side note, DON"T flash different roms without wiping all including System 3 times before flashing--prevents a lot of problems
Click to expand...
Click to collapse
thank you very much
i already tryed everything else what you wrote but i didn't wiped 3 times... after erasing recovery partition 3 times i was able to flash a new recovery and it started.
Thanks a lot!

Glad that you got it

[Q] N4 stuck in boot loop after OTA update

Hello,
I saw that the OTA update to Lollipop was available on my phone today, so I went ahead and let it download. Upon completion of the download, it restarted and applied patches, then restarted again and has been stuck in boot loop for about an hour. After reading several other threads on how to try to reset the phone, I'm stuck. When I try power + volume up or down, the LED status indicator flashes red and I never get to any kind of other screen. Am I completely screwed? I previously had stock 4.4.2 with no modifications.

Finally was able to get to the bootloader menu. Apparently having the phone plugged into the charger was preventing me from getting there for some reason. I ended up having to wipe the phone to get it to boot

so you can get into clock recovery right? download nexus 4 toolkit..that might save your phone. I suggest you to unroot and flash everything to stock and then unlock again and start everything from scratch. good luck.

Similar issue on an OTA upgrade to an unrooted N4. It's stuck on the Lollipol boot screen with the rotating Circle thingies.
I can get to the Android System Recovery but there's no CWM or TWRP on my N4. I'm guessing a factory reset will fix it but is there a way to preserve my pics/files on the phone before doing so?

Sportfreunde said:
Similar issue on an OTA upgrade to an unrooted N4. It's stuck on the Lollipol boot screen with the rotating Circle thingies.
I can get to the Android System Recovery but there's no CWM or TWRP on my N4. I'm guessing a factory reset will fix it but is there a way to preserve my pics/files on the phone before doing so?
Click to expand...
Click to collapse
I guess TWRP Recovery has option to enable MTP and you can access the internal SD card by connecting mobile with computer using usb cable.
---------- Post added at 06:37 PM ---------- Previous post was at 05:37 PM ----------
Sportfreunde said:
Similar issue on an OTA upgrade to an unrooted N4. It's stuck on the Lollipol boot screen with the rotating Circle thingies.
I can get to the Android System Recovery but there's no CWM or TWRP on my N4. I'm guessing a factory reset will fix it but is there a way to preserve my pics/files on the phone before doing so?
Click to expand...
Click to collapse
Flash TWRP Recovery using fastboot.
1. If you have otg y cable, connect it and use file manager to copy all the files.
2. OTG method is failed then select “Mount”, then select only “Data” and connect your Nexus 4 to your computer and Enable MTP in TWRP. now you can use adb pull and push commands.

I ended up going the factory reset route, which wasn't really a bad thing. My photos had been backed up in dropbox and the play store remembered all the apps and were able to reload them. The only things I really had to do was reload some music onto the phone and re-enter passwords for apps.

Same story here: sideloaded the OTA zip file, then had bootloop. Tried a few approaches, but none worked. In the end only wiping the data was the solution for me. Lost some userdata in a few important Apps...

I went through this yesterday. The only way to get it to boot is a Factory Reset from Recovery. It works like magic, but sucks you lose the data.

Got the OTA yesterday and also got a bootloop(stuck in boot screen animation). I couldnt afford losing my photos/videos as i had no backup , so i figured out a super easy to get it to boot without wiping data .
I was unrooted with stock recovery running stock 4.4.2, bootloader was unlocked. I flashed CWM recovery through fastboot and wiped chache+ Dalvik from there then simply rebooted the phone .
I had already tried wiping cache from the stock Android recovery,needless to say that didnt work for me.
If anyone else is having the same problem please try the method above and report back, cheers!

I post this on Google Product Forum 2 days ago. Hope it helps
https://productforums.google.com/for...Q/wDzRUm4b2UsJ
(updated 29/11/2014)[not perfect but it is a SOLUTION]
The idea of this is to downgrade your nexus 4 without wiping your data, which means stuff you will need includes:
1. adb and fastboot on your computer (I am using mac but you can find it on windows as well. There are tones of website and forums telling you the latest method of getting it onto your computer)
2. factory image of nexus 4(I use 4.4.4, since that's what it was. I don't have the time and energy to try to do the same thing with lollipop. you can try can leave a comment).
update: do NOT try to flash 5.0 rom using this method. You will be stuck at boot loop again
3. usb cable
4. nexus 4 with unlocked bootloader(the process of unlocking bootloader will wipe your device)
5. computer
steps
1. unzip the factory image (something.tgz)
2. for me, after unzipping the .tgz, I still find another .zip inside. unzip that too.
3. hold vol+, vol-, and power button simultaneously to enter fastboot mode
4. open terminal(mac)(it would probably be cmd for windows)
5. connect your nexus 4(in fastboot)
6. to make sure it connect successfully, type "fastboot devices". if something like "005040c0d54bb291 fastboot" appears, you are good. Otherwise, try reconnect your device/boot to fastboot again/use another usb cable
7.now we need to tell the terminal to navigate to the location of the unzipped factory image. to do that, i suggest you put the unzipped folder to somewhere easy to find, like desktop. these are some commands to help you navigate:
"ls" allows you to look at whats inside the current directory of the terminal. For example, this is the output after typing "ls" for me:
some folder Photos
nexus4image.tgz how many folders do you have
5.zip occam-ktu84p
more folder occam-ktu84p.zip
after knowing where you are, use "cd" (below) to go to your folder
"cd" means change directory. For example. "cd Photos" will brings me to the "Photos" folder. And then if I type ls, I will see a whole bunch of photos in my photos. If you go to the wrong folder, type "cd ..", and it will bring you back to the previous folder.
8. flash bootloader.
enter the following command, BUT REMEMBER TO CHANGE THE NAME TO FIT YOURS(DIFFERENT VERSIONS HAVE SLIGHTLY DIFFERENT FILE NAME AT THE END(type ls first to help you type the correct name)
fastboot flash bootloader bootloader-mako-makoz30d.img
9. reboot bootloader. just copy and paste
fastboot reboot-bootloader
10. flash radio
enter the following command, BUT REMEMBER TO CHANGE THE NAME TO FIT YOURS(DIFFERENT VERSIONS HAVE SLIGHTLY DIFFERENT FILE NAME AT THE END(type ls first to help you type the correct name)
fastboot flash radio radio-mako-m9615a-cefwmazm-2.0.1701.03.img
11. reboot bootloader. just copy and paste
fastboot reboot-bootloader
12. flash system
system.img is located inside the zip, use ls to help you navigate. This steps takes the longest time, total time on this step is 87 seconds while the others are less then 1 second
fastboot flash system system.img
13. flash boot
boot.img is located inside the zip, use ls to help you navigate.
fastboot flash boot boot.img
14. flash recovery
fastboot.img is located inside the zip, use ls to help you navigate.
fastboot flash recovery recovery.img
15. format cache(not the memory, so everything should be fine)
fastboot format cache
16. reboot and wait
this will reboot your device. You probably have to wait for a while to initialise all the apps. after than you are good to go!
fastboot reboot
credit: my friend for giving me this idea + http://forum.xda-developers.com/nexu...image-t2010312 + HelpMyNexus

phone bricked? help!

I decided to update my old oneplus 2 to lineageos 15.1 with, but when I tried to flash the file with TWRP, it shows an error. Since the TWRP version I was using was old, I decided to update it first. Keep in mind at this point i had completely wiped my device. So, I downloaded the "twrp-3.2.1-0-kenzo.img" file, as per a youtube video where the dude managed to flash the update successfully, and gave it a go. It showed up as successful. Then i shut the whole device off, and tried to boot back in to recovery to flash the ROM again, but the thing won't boot. It's stuck on this boot screen (with the oneplus logo and 'powered by android' at the bottom), and refuses to go further. I'm stuck in a situation with the phone having no OS, no recovery and the thing won't show up when I connect it to the pc either. Well, the pc makes the 'device connected' notification sound when I plug it in, but nothing shows up on the file explorer or the device manager.
That's my dilemma, please i need help!
Thanks in advance.

inwarse said:
I decided to update my old oneplus 2 to lineageos 15.1 with, but when I tried to flash the file with TWRP, it shows an error. Since the TWRP version I was using was old, I decided to update it first. Keep in mind at this point i had completely wiped my device. So, I downloaded the "twrp-3.2.1-0-kenzo.img" file, as per a youtube video where the dude managed to flash the update successfully, and gave it a go. It showed up as successful. Then i shut the whole device off, and tried to boot back in to recovery to flash the ROM again, but the thing won't boot. It's stuck on this boot screen (with the oneplus logo and 'powered by android' at the bottom), and refuses to go further. I'm stuck in a situation with the phone having no OS, no recovery and the thing won't show up when I connect it to the pc either. Well, the pc makes the 'device connected' notification sound when I plug it in, but nothing shows up on the file explorer or the device manager.
That's my dilemma, please i need help!
Thanks in advance.
Click to expand...
Click to collapse
You downloaded the KENZO (this is not oneplus2! ) TWRP and flashed it on another phone (oneplus2), just normal that it doesn't work and your phone is messed up.
If you can enter fastboot (vol up and power button to boot) you can rescue your phone:
-enter fastboot (vol up + power, while phone is completely off, u can also hold it until you can see "fastboot" written on the screen)
-connect device to a computer with fastboot installed
-type "fastboot oem unlock" into a terminal/cmd window if there is no error, you are good to go, otherwise your bootloader relocked, use this thread to recover
-if your bootloader is still unlocked, download the ONEPLUS2 TWRP IMG, ALWAYS make sure to only flash the roms, kernels, recoveries or zips for YOUR phone otherwise you can really DESTROY your phone!
-now type into terminal/cmd: "fastboot flash recovery *drag the oneplus2 twrp image into terminal/cmd window* and hit enter
-use vol down + power to reboot phone into recovery and wipe all partitions
-Install a ONEPLUS2 ROM of your choice
If something is not clear, use google, because this is most likely basic stuff you have to know when flashing your phone

I can in fact go to fastboot mode by holding the power+volume up keys. When I the phone to my pc it does show a fastboot device (9597b869 fastboot). What do i do from here?

inwarse said:
I can in fact go to fastboot mode by holding the power+volume up keys. When I the phone to my pc it does show a fastboot device (9597b869 fastboot). What do i do from here?
Click to expand...
Click to collapse
As I wrote above (it's a step-by-step guide, u only have to READ )
-connect device to a computer with fastboot installed
-type "fastboot oem unlock" into a terminal/cmd window if there is no error, you are good to go, otherwise your bootloader relocked, use this thread to recover
-if your bootloader is still unlocked, download the ONEPLUS2 TWRP IMG, ALWAYS make sure to only flash the roms, kernels, recoveries or zips for YOUR phone otherwise you can really DESTROY your phone!
-now type into terminal/cmd: "fastboot flash recovery *drag the oneplus2 twrp image into terminal/cmd window* and hit enter
-use vol down + power to reboot phone into recovery and wipe all partitions
-Install a ONEPLUS2 ROM of your choice

wertus33333 said:
As I wrote above (it's a step-by-step guide, u only have to READ )
-connect device to a computer with fastboot installed
-type "fastboot oem unlock" into a terminal/cmd window if there is no error, you are good to go, otherwise your bootloader relocked, use this thread to recover
-if your bootloader is still unlocked, download the ONEPLUS2 TWRP IMG, ALWAYS make sure to only flash the roms, kernels, recoveries or zips for YOUR phone otherwise you can really DESTROY your phone!
-now type into terminal/cmd: "fastboot flash recovery *drag the oneplus2 twrp image into terminal/cmd window* and hit enter
-use vol down + power to reboot phone into recovery and wipe all partitions
-Install a ONEPLUS2 ROM of your choice
Click to expand...
Click to collapse
i tried to follow the guide. but the bootloader, as per you description is relocked. the download link for the driver you provided shows up as empty/no longer available. that's where i'm getting stuck.
P.S, i can enter fastboot mode on the phone via power+volume up.
thanks for the help so far, i can't seem to find much help other than from you so far

Oh, the link is dead, sry for that. try this one (GDrive links are up and working).

inwarse said:
i tried to follow the guide. but the bootloader, as per you description is relocked. the download link for the driver you provided shows up as empty/no longer available. that's where i'm getting stuck.
P.S, i can enter fastboot mode on the phone via power+volume up.
thanks for the help so far, i can't seem to find much help other than from you so far
Click to expand...
Click to collapse
so i managed to get into qualcomm mode, updated the drivers, and ran "MSM8994DownloadTool.exe" in administrator mode. it went as it's outlined in your guide. however, at the end of that process, the phone got stuck in a bootloop (the oneplus logo flashes for a moment and restarts). and can't get into qualcomm mode now, since when i connect the usb to the pc while the phone off, it lights the display (to show that it's charging, i think). any way back from this?
(i can still get into fastboot mode)

inwarse said:
so i managed to get into qualcomm mode, updated the drivers, and ran "MSM8994DownloadTool.exe" in administrator mode. it went as it's outlined in your guide. however, at the end of that process, the phone got stuck in a bootloop (the oneplus logo flashes for a moment and restarts). and can't get into qualcomm mode now, since when i connect the usb to the pc while the phone off, it lights the display (to show that it's charging, i think). any way back from this?
(i can still get into fastboot mode)
Click to expand...
Click to collapse
Do you still have TWRP? If yes go to TWRP and shut down the phone there, afterwards you should be able to enter qualcomm mode again.
otherwise you have to try (i think 10s power button will shut the device completely down). You should be able to enter qualcomm mode if the device is fully shut off (your scenario sounds as if the device is not fully shut off when u connect it to the pc).
Just to go sure: You are absolutely sure to have a oneplus2, are you?

inwarse said:
so i managed to get into qualcomm mode, updated the drivers, and ran "MSM8994DownloadTool.exe" in administrator mode. it went as it's outlined in your guide. however, at the end of that process, the phone got stuck in a bootloop (the oneplus logo flashes for a moment and restarts). and can't get into qualcomm mode now, since when i connect the usb to the pc while the phone off, it lights the display (to show that it's charging, i think). any way back from this?
(i can still get into fastboot mode)
Click to expand...
Click to collapse
Could you resolve the issue?

wertus33333 said:
Could you resolve the issue?
Click to expand...
Click to collapse
nope. kept running into issue after issue, so got dejected and gave up.

How I managed to flash LineageOS on my LG G5 (H850)

I post this because none of the guides on the internet worked for my phone, and I had to cut my own way through the jungle. Maybe, this helps someone out there. I have found it extremely difficult to flash LineageOS on my LG G5 (H850). It seems that LG changes that device every now and then, and the installation guides on the internet do not fit any more. Flashing Cyanogen on my Samsung S2 was a cakewalk compared to this.
Here is how I - finally - managed to flash LineageOS: I will explain it as a modification to LineageOs.org‘s installation-wiki for the LG-H850 (wiki.lineageos.org/devices/h850/install) and for Linux.
Firstly, I had difficulties with fastboot. It does not work just to download adb and fastboot. You have to properly install them so that you can run them from any directory. Installation guides are all over the net. Fastboot can only be used when you are in the bootloader. That means you have to run „adb reboot bootloader“ first. Other than adb, you have to run fastboot as administrator (i.e. sudo fastboot devices). You will probably forget adding „sudo“ every now and then.
Trying to tackle my fastboot problems I installed the entire Android SDK; I do not know if that is a requirements. People discuss driver problems; fastboot seems to use other drivers than adb. However, from what I can tell the core-issue is to run fastboot as administrator.
Secondly, rebooting into recovery is also extremely tricky. Entering recovery worked for me by pressing volume down + power and releasing only power for a blink of an eye once the LG logo appears. Most instructions tell you that you will enter a fully-fledged recovery menu. My phone presented me a menu which only offered factory data reset. That you have to do although one hesitates to reset the phone.
However, this will only bring you into the TWRP recovery when you earlier have taken the correct exit after flashing TWRP. You should not have left the bootloader by entering „sudo fastboot reboot“, which will simply restart your phone and you have to shut it down again after it has rebooted. If you enter recovery and do the factory data reset then, the phone will not go into TWRP recovery but simply do a factory reset, and you can start from the scratch.
Instead of rebooting, I had to end the bootloader by disconnecting the battery. When I went into recovery by using the above button-combination and did the factory reset, that lead me into the TWRP recovery menu.
Another lesson I have learned is not to use the system update but to run updates manually through TWRP recovery. The system update does not work properly, and the phone will keep booting into recovery. Another flaw well documented all over the net. And don‘t forget that you have to become a developer and to enable debugging again before you can use adb to manually access recovery...