[NEEDS INFO] Performance

I have noticed a large performance decrease after I changed the video and graphics settings a few times. I set the max. FPS to 60, but they actually haven't even reached 20. A hard reset of the game helped out, but is there an easier and faster way?
Have/had some of you the same problem? How did you solve it?

This could be very dependent on maps, especially ones that didn't ship with the game. Can you tell us more about your hardware?