I bought a HDMI switch to switch between this win 10 PC and linux laptop. The switch is garbage and so I'll send the switch back.
My win 10 machine is attached to my monitor with an HDMI Cable.
Every time I boot this machine the settings in the resolution field is 1024*768. There is only one other option: 800*600.
I have a GTX 970 installed with 388.13 (apperently newest) installed.
Stuff I figured out
If I attach this PC to a TV, the resolution jumps to 1920*1080. While running I I'll detach the cable from the TV to my Monitor and then I also the expected resolution of 1920*1080. But only for as long as I don't reboot the machine.