Ok fixed it. But i had to flash the Android 9 Developer Preview via fastboot to acces the phone again.I used 3.2.2-0!
Now after Factory reset and format system twrp is no longer there. Just fastboot mode. When i flash twrp with Linux terminal it works but i can not boot into it. Just fastboot mode... FCK
Where? no sourceforge linkThere's a MI8 ROM on SourceForge