First off - great game for a 600. Also understanding that around that area is where things went wrong is good on your behalf.
I could explain better ways to continue after 19, but as a human I'd like to recommend what GM Finegold always says: never play f6.
I do play f6, but only in situations I've analyzed before, and know that f6 is like a boss move, know as in - it's an objective fact. (Like in Ruy Lopez Exchange, Lines in Nimzo-Larsen, Lines in Bishop's Opening, etc...)
Otherwise, if at some point in a game I want to play f6 and it's a position I never seen before - I just don't play f6, like 99% of the time. It's a dangerous move that exposes your king most of the time.
Also avoid having a backwards center pawn (your d7 pawn is kindof awkwardly stuck, because you chased his Bishop)
So while you were busy wasting time (tempo in chess) chasing White's Bishop,
White took over the center! the center is important.
Therefore 9...b5 was not a good move. and 18...f6 was a really dangerous move.
So I'd take away these principles:
- Never play f6
- Don't chase pieces unless you gain something concrete from chasing them and do not lose Time...
- think about Time in general in games (which White didn't lose btw, cuz his move e4-e5 gained several things: 1. Time on your knight, & 2. Space against your backwards pawn 3. central control, making your position uncomfy)
- Control the center - that means you need to either put pawns in the center or place pieces attacking the center or prepare to place pieces to attack the center (fianchetto... etc) if a move in the opening does not do these things - it might be really bad!
Cool game and I can analyze other parts of the game later if you like...
Cheers!
Here is the game. I understand moves from move 19 were bad, but I don't understand engine moves mentioned before. The early Nxe4 could have been played. I also understand that, it's the moves in between I am unclear on.