So, the same as all of you guys, I also suffered the major problem in the game which is Low FPS or sudden FPS Drop. I've been looking for the solution all day long and try all of it in order for me to play smoothly (at least 25-30 fps) and IT WORKS! I don't know which one really works for me so I will put all the things I did below:
*note: It might be not the best graphic mode, but at least you can play smoothly. AND THIS TUTORIAL ONLY APPLY TO FIX FPS PROBLEM not other problems (like crash or static sound etc.)