I did that but it didn't help... but I'm 1 step further:
I deleted partition 1 (the efi partition) and then continue.
Then I get a warning about the EFI, I continued and it worked.
Now I get a problem with the GRUB:
The 'grub-efi-amd64' package failed to install into /target/. Without the Grub boot loard, the installed system will not boot
BTW:
Boot Mode UEFI Only is black in the BIOS (not editable)