E on H815 failed, cant log in

Hi all
I have been using my LG G4 H815 single sim since Nov. 2021. So far I never made an update. As I am off today, I thought, time to change that. So I follwed the guide here up to Step 3 " Once downloaded, tap on Install. Tap on OK to start the installation.". Then I waited, waited, waited, went biking, nothing. So I thought, I need to reboot it myself. Shut it down, took the sim card out, as needed to make some calls on an another handy. Started my H815, it boots, shows the bouncing e, prompts for my key and then nothing. It just goes black again. I can tap on the power button, key in my pin again, same story again.
How can I get my beloved H815 on e alive again?

If I switch it on, I can enter the pin and get to the desktop. If it blanks again, I can reenter the pin but not get to the desktop again. If I issue a restart, be real fast entering the pin, it says Settings" repeatedly terminated (in German), also “torch” repeatedly terminated etc. Camaera app starts though, calc too and maybe others.
To me that looks like the update did not complete successfully. If, how can I reinvoke the update process?