100% CPU and Low FPS on Rust

Hello

I have some big problems with Rust, in the begging when i connect to a server i got around 60FPS but after some minuets the FPS going down to around 5-15.
I have read on some forum treads that you need to select which graphics card rust should use, when you have a graphics card integrated into the motherboard, I have deactivate the integrated graphics card but i still got the problems

Here is the specification of my computer

Motherboard: Gigabyte Z97X-Gaming 3

I also took a screen on the Resource Monitor

I have also tried to set down the graphic settings to the lower, still the same problem

does anyone have any solution of this problem?

Thanks!
//Limme