I started the predownload once again, now i said "no" to uninstall the previous version but the version remained the same: 2.55
I´ll guess the best is to manually uninstall all FH2 stuff before than anything else.
I´ve installed the predownload and clicked on uninstall previous version which you shouldn´t. After that i started the FH2 Launcher like it was recommended on Discord.
The game works but i had a lot of disconnects.