Fps problems

Hi guys my fps is usally around 30-40 , and my settings on low and best possible things to increase it (except the screen resoloution) , you gusy got any tips on how to boost it?

Also my bigger problem is when i fight somone my fps goes to like 10-14 and i usally lose fight because of how laggy it is , and it happense evrey teamfight, you guys got any solutions?

Thanks!