I would actually say that your endgame is weak and needs improvement. The reason is: you play moves with out realizing the serious pawn structure repercusions and thus fail to see their actual dynamic potential. All I see is that you failed to fight properly for the d5 square after playing e5. End result you have TWO backward pawns on open files and a lost (or close to it) endgame. I think your opponents move 30. Was a blunder giving a beautiful knight for a horrid bishop.
Positional books and endgame books can help you. "Simple Chess", "Chess fundementals" and any endgame book. I would also reccomend you to play more classical openings where positional themes are easy to catch on.

. I probably shouldn't have even moved that queen in the first place :(
So here's a recent midgame of mine. I chopped off the endgame because it's irrelevant for my purposes :). Any help would be appreciated because I KNOW i didn't come up with the sharpest possible variations :(