So a reinstall of Windows 10 on the SSD helped and now i can boot the OS from the SSD, but the SSD still isn´t listed at the BIOS boot section and i still have to choose where i want Windows to boot from before start. As others complained here at the Forum, the Sounddrivers were missing, but i fixed it in the BIOS. I hope i can fix the Problem with the multiple Windows because this could be really annoying in the future..