I forgot to add, the device can be started and it boots normally after like 5-10 seconds, but this happens again every reboot or when i try to get to recovery. That was my mistake, sorry.
I flashed it with "fastboot flash recovery twrp....img" command. After this, the phone rebooted and I ended up in that screen.
I don't really know, what went wrong since I am sure I had the right twrp.