As a Class B, how do I improve my chess against A level or higher? I been playing bunch of tournaments where I have solely played against Class A. I keep losing or drawing against Class A players. I draw when I'm winning. Sometimes I don't understand A players moves in the middle game. I struggle understanding what plan a given position needs or what plan my opponent has in mind. Even if I figure out their plan, I play the wrong move to stop them. Sometimes I'm winning, but A players have really strong counter-play and I lose to their counter-play. My endgame is my strongest feature, but I usually get to a losing endgame. Any advice?
Silman's How to reassess your chess book is invaluable. Give it a thorough reading if you haven't yet.

My advice would be


Replay your game with an engine. Find out the moves you did wrong.
if most are tactical, then train yourself on that
if most are positional, then find out what imbalances are there at your move. Read relevant chapter in the book (could be just the summary section) and see if you can find a better move.