Simple, yet effective! This did the trick. Removed all but 1 RAM and cpu, could enter bios again. Added the gpu, still worked. Then first i added the drive with the windows partition, could boot into windows again. Afterwards all the other drives, and if i select ubuntu in bios boot order, im shown the GRUB that lets me select my OS, and both OS work without further problems.
Thank you very much!
I mean dead cells is a great game and so on… But a soulslike?