Like in the subject, i remebmer FC3 runs horible on DX11, when i turn it of it was waaayyy better and even i was able to run some other options.

It's not possible. You need a DX11 card to play, therefore you can't turn DX11 off. Sorry, mate.

Like in the subject, i remebmer FC3 runs horible on DX11, when i turn it of it was waaayyy better and even i was able to run some other options.

There is no off because Crysis 3 only ships with DX11 hardware support.