play many many many games
how to improve???
I used to read the book “the art of combination” and do the puzzles in the book. You may start with easy ones first.
The puzzles will help you catch your opponents’ mistakes faster and more accurately. I’m still doing puzzles daily to improve my skills. Hope my suggestion may help you.

Except books can I do anything else to improve???
Play long time control games. Look at a lot of GM games. Save positions and games that you find instructive and review them again from time to time.
Also solve a lot of tactics puzzles.

By the way, the main point of looking at GM games isn't to understand every move. Don't do that because you'll only frustrate yourself and give up.
The point is to connect a middlegame idea to an opening. For examples in the sicilian dragon you might notice black often attacking on the queenside. So it's like that. Identify an area (kingside, center, or queenside) and the general method (pawn breaks and piece placements).

Three things I think you should focus on:
Tactics (Training), Opening Theory, & Endgame Study.
#1. Tactics/Puzzles:
Chess.com has free puzzles that you can do to help your tactics. These puzzles will drastically improve your critical thinking skills at chess. You can do puzzle rush, puzzle battle, and puzzle training (rated/unrated). Just click 'puzzles' on the side bar and begin training!
#2. Opening Theory:
This is really important. You need to know this to not fall into a trap, build a strong center, and get a good position overall. I suggest reading some solid chess books, as well as surfing the Internet.
#3. Engame Study:
Perhaps the most important of all. Knowing how to convert a good endgame position to a win is vital. You definitely should read quite a few books on this subject, as well as watching some reliable videos.
Thanks for reading this . Hope it helped!
Good luck on your journey,
@Aida_Amin

I am not a beginner but i know basics and i am learning now in chess.com.But I want to improve.All my friends who were same as my rating has improved.Is there any way to improve my ratings???Except books can I do anything else to improve???
Play slow time controls.
Take your time when solving tactics.
Follow opening principles.
Do your own analysis.
Use an engine ONLY to check for blunders, and missed tactics.
I am not a beginner but i know basics and i am learning now in chess.com.But I want to improve.All my friends who were same as my rating has improved.Is there any way to improve my ratings???Except books can I do anything else to improve???