how do i improve in chess?

I  am 11 have been playing for  around 4 months now and i haven't made lots of improvement even though i have been playing chess more recently and getting better even though i am quite bad , and my only teacher, my grandfather died on the 3rd and i would like to have some tips on mastering endgames and opening 

thank you 

There is one rule that helped me out a lot when it comes to rating.

When your opponent moves you must always ask yourself: "What do they want?"

You always have to be mindful of your opponents plans as well as your own.

For openings I recommend studying the Vienna Game. The Vienna Gambit, and the Vienna Game: Max Lange Defense, as they will work at almost all elos (Chess rating) and it's easy to remember.

For endgames, learn simple mating patterns, and I recommend going to Lichess.org for free puzzles, not only on the endgame but to learn simple tactics.

Best of luck.

there ia help for you check this blog

 https://www.chess.com/blog/hkchessking/how-do-we-improve-at-chess-for-people-who-are-stuck-in-their-rating.

Play

I have been playing Chess for a while with my dad and I think that experience is one way and you should also do the Chess.com puzzles if you are looking to improve.

Have you went through the chess.com guide tutorials or the 50 openings tutorial? Go through them several times until the names and moves look completely familiar. Once you do that you will be able to understand the more complex tutorials. That being said everyone has opening issues, and middle game and endings. And there is a tutorial in a few places on opening traps; sometimes it is better to understand what not to do.

As for the aftergame, Remembering your play as better than it was afterwards and bragging to your friends that part is easy.