Tips to improve middlegame?
you need to do puzzle rush survival everyday. you also get 3 free puzzles everyday. also goto learn lessons library and type in ( use your pieces tactfully ) by dejan , you could also goto learn lessons library and guide, do all intermediate and advanced lessons ( you get 1 free lessons per week, sometimes more) . after that goto learn practice and drills, do all that you can. once you are done with these let me know.
Pawn formations in the center are the single biggest determinant of middle-game play.
Read "Pawn Power in Chess" by Kmoch, or Pawn Structure Chess" by Soltis for more info on that.
Read this thread of mine. Posts #4, 7-to-10 and especially post 12.
Then play over the three sample games on page 1 and 2 of the thread, reading the notes.
GM Larry Evans' method of static analysis - Chess Forums - Chess.com
Tips for middle game?