Buy new PC.
How can we fix something, if you don't have any real issue? Lags are caused because your gear is too old. Try leatrix latency fix, that might help, clean your PC from every unwanted program, or even better, re-install the windows, add leatrix latency fix, then try to play normal again. If you still can't play normal after that, the only solution is the first sentence of this post.