3...b6 is a little weird because you usually want to develop the pieces very quickly in open games and ...b6 and ...Bb7 is a little slow. It's not a mistake or anything but moves like 3...Nc6 and 3...Bc5 are better because they facilitate quick development of the pieces. 3...Nxe4 is also possible but tricky.
5...exd4 is the way to go. After the forced 6.Qxd4 and then 6...Nc6 you develop with tempo because White's queen has to move again. I'm not sure if 5...Nc6 6.d5 Nb8 is a problem though. Maybe someone else can chime in on that.
7...Nxe4 unfortunately doesn't work tactically. Be careful about munching pawns when your king is in the center of the board. There might be traps waiting. 7...Bb4 developing a piece and pinning the knight looks good to me.
11...Nxf3 actually loses two pieces instead of one. Maybe 11...O-O-O is better just getting the king out of the center and getting a rook out. Because you'll be a piece down you'll have to do everything you can to try and get at White's king on f1 because it's the one problem in his position.
18...Rd8 pins White's bishop and wins one piece back.
20...Qc1 looks better because the queen has more squares it can move to than from b1.
27...f6 protects your hanging pawn on f7. The knight on g1 can't move now anyway because the pawn on h3 is loose. After 27...Rh1 your rook is a little short on squares to go to.
I think 29...Kc8 is good getting the king into the game. Piece activity is really important in endgames.
30...Kc8 is the way to go. You want your king moving close to the center of the board where it can be active and possibly support your pawns.
Maybe 33...Rc5+ and then 34...g5 or 34...h5 is better. The move 33...g5 cuts your rook off from the action.
The problem with 36...g4 is that the pawn can't queen on it's own. You have 3 passed pawns so try getting them to work together with something like 36...h5.
39...h5
42...c5
45...Ke5 hits the knight again. Then 46.Kg4 h5+ and 46.Ne3 Rc3 47.Kf4 Rxf4 48.Kxf4 Kxd5 win. I think you're still winning with your move because threre are too many pawns spread across the board. I could be wrong though lol.
I think if you try to play more for piece development, activity and king safety you'll be fine.
I think this game was all luck on my end.