Three years, thousands of games, no improvement?

If you look at this position, the best moves white will be planning are

1. a3

2.b4

3. Bb2 etc.

However, white plan 1. a3 can be immediately stopped by black pushing " d5".

That is what we call, " missing tactics". Any good plan will be immediately ruined by not seeing opponent counter moves.

That is why Stockfish kick out Bishop on a6 by Qa4.

So Qa4 is a must. 

Simple technique in checking engine moves, dont follow engine moves and do whatever you plan. Engines will suggest counter moves that has flaws on your plan.

There you go, I was looking at this the wrong way then. I thought that it is a positional thing and a gain of tempo. Planning is something players our level lack in many cases, and it takes time to learn. But what you say about this plan makes sense. Thank you for taking the time to answer.

On this position, according to Stockfish recommendations,  white plan is to play " c5", keeping black  "d" pawn backward. If black move that pawn, " c" pawn will be isolated.

Very interesting. b4 seems a bit more straightforward at least to me, but yeah this one has merit. b4 seems to have a similar result in the end of the line (b4 then c5 and the result with the d pawn is the same). The reason why this looks more straightforward (subjectively for me) is that in this Nb3 line c5 is pretty advanced and I would be worried that it doesn't become overextended - even though it is not easily attacked multiple times.

PEOPLE WHO GET STUCK AT A RATING BELOW 2000 ARE MAKING THE SAME MISTAKES OVER AND OVER AND OVER AGAIN. 

THJE PROBLEM IS THEY DO NOT REALIZE MANY OF THEIR MISTAKES.

YOU NEED TO REALIZE YOUR PROBLEMS AND TAKE STEPS TO FIX YOUR COMMON MISTAKES.

['SORRY FOR CAPS--I HAVE MEDICAL PROBLEM,]

You won’t improve unless you dedicate yourself to studying.  You need to study tactics, endgame play, and you need a solid understanding of strategy/positional play.  You need to study these things relentlessly.

You also need to learn to calculate at least 5-6 moves ahead for each side.

Finally, you’ll need to study master and grandmaster level games.  Real improvement takes hard work.  Most people don’t want to put in the work needed to become a strong player.