Thanks to everyone who considered helping me with recommendations. Never ever boost but minimize Terrain Level of Detail if you want a good FPS on high settings.
Also reinstalled Contents folder then turned off my pc for a while, then found that solution.
In your Nvidia control panel .
Or display properties advanced tab in 
Windows
Problem seems to be temperature because first few minutes my FPS is too good then goes below, I think a cooler can help. Also it is the level of detail settings causing big majority of issue.