FH5 unplayable because the game dont want to use 100% of my GPU

Hey,

i have this wierd problem that when im ingame (maximized and windowed) my GPU only got to 24% and my fps is 15, but when im tapped out it will go to 100% GPU usage and my fps go up.
But when i tap in it goes down.

Hey.

What GPU do you have? Drivers are already updated?

I got an Asus GTX 1080 OC with Nvidia 496.49.
It is the latest driver.