The issue here isn't that there were good moves played by black, in a tactical sense - these moves are obvious to plenty of decent players, and they could easily find them without an engine.
What is surprising is that your opponent hung an exchange, apparently not seeing it. This indicates a very poor tactical skill. So it's very hard to imagine your opponent playing the way he/she did the rest of the game. It's inconsistent.
Still, you can't conclude anything based on a single game.
I was winning.
After I took his rook with my bishop, many of his moves were the first/second/third choice stockfish. The super move e3 that cost me the game was the first choice of stockfish.
You tell me. The move lc4 to prevent taking the queens from the board was very nice. The first choice of stockfish. But this doesn't mean my opponent used an engine. Just the sudden e3 super move amazed me and made me wonder, did my opponent use an engine?
If my opponent didn't use an engine, he just played awesome. He didn't fall for my trap, in which I invited him to take my rook with his horse, instead he played pf5 on move 18, which was the first choice of stockfish.
By the way, I edited the name and the rating so that it doesn't lead to the player I played against in this game.