I have installed a stock firmware and booted twrp as follows.
fastboot --disable-verity --disable-verification flash vbmeta vbmeta.img
fastboot boat twrp.img
I started twrp as Read only and made a backup of the partitions via terminal and dd.
When I wanted to restart I had a bootloop.
I actually only started twrp, not flashed it... Does anyone know?
In the end I just want a backup of the pure stock firmaware.