DualBoot Debian/Windows Keyboard does not work at boot

[papst]

So I am using mainly Linux but you know sometimes you need Office Programs etc.
I thought that a dual boot system would be good so I installed it but it really weirdly bugs. When I boot my PC in the morning when it was for like 10 hours I literally cannot control the keyboard, it just does not get detected not even bios boot is possible, so I need to wait for Debian to boot and restart to have a keyboard again and choose my OS via GRUB.
However when I only install Windows or Linux (one OS on the Disk) all works great which really gets me off.

My Hardware:
ASUS ROG Strix Z390-E
Intel Core i9-9900K
GTX 1080
1TB NVME

Help would be very appreciated since this torments me for 2 weeks already.