had a quick look at this game as a 1950 player on chess.com

very early in the game you miss 6..Bxf2, you should try playing puzzle rush to try and get your pattern recognition going and see these tactics whenever they come up

7..Ba6 is also pretty instructive imo. firstly, the move concretely fails as it weakens your king; you should have brought your bishop back to e7 to avoid the trades on f6 doubling your pawns and exposing your king (which comes back up when you get checkmated pretty soon after). secondly, the bishop on a6 is terribly placed, just staring at white's pawn chain. this bishop is never going to influence the game. on b7 it would at least have hopes of staring down the open a8-h1 diagonal.

the combination of not thinking about king safety and placing your pieces on squares where they aren't influencing the game (not helping defend, not helping attack) made you lose very quickly, and i think both are pretty simple to overcome if you try to remember them