Etcher, Balena-etcher, Unetbootin, Rufus, Multiboot USB... We all have our preferences. I can only suggest finding one that you feel fits you best. They all mostly work.
Mostly...
It is best to disable Secure Boot. Even if you end up needing to enable it again later, keeping it enabled during installation can cause a lot of problems.
As @carmar suggested above, you can select Something Else (Etwas Anderes) to open the Partition Manger. In this screen, examine carefully what disks are being recognized - But do not install yet until we know better what is going on.