@bruce_wayne1 1) You lost momentum in the middlegame bcs of unnecessary captures and retreats with your knights. Knight manouvers should be done after everything is developed and the center is fixed and the knight not needed where it is. If you manouver your knight try to not do it by jumping back to the initial square.
2) The endgame is slightly better for black as:
- Black's king is much more active and also defending his pawn weaknesses
- Your knight is busy defending the second rank from the rook infiltrating
- Bishops are slightly stronger when there are pawns on both sides of the board
- Your pawns are currently under attack, black has the initative
- Your rook isn't as dangerous as black's one as he has no targets to attack
You don't need to worry that much about advantages of -1 in the endgame at your level. This can still end in a draw.