Already did thx.Well, at first glance everything is ok.
So ideas are to try FORMAT DATA after Havoc has been installed and try some another TWRP version.
I use ROS now. In ROS I need to flash Okita to solve some bugs.
The interesting part is, that I directly flashed Okita after the rom and the bugs were not solved. After reboot and flashing Okit again it works.
So it seems that the kernel will be flashed only after a reboot - idk why - and that´s why the fastboot problem persists.
I can wait and check out ROS. Thank you for your work and help!