I tried both, the OpenGL option didn't let me play at a stable framerate in SP and didn't work as a solution at all.
Reinstall also did not help me with the issue.
Yeah, i had steam open and yes, i ran the launcher as Administrator
Only one thing i have not tried yet - reinstall the game itself - but i think it's kinda drastic and i will consider it if i don't solve the solution anytime soon.
thanks for your help everyone, i am still open to suggestions