Puzzle Problem Explained

Hey, please help me! I had a bad day again with this puzzle problem.

In this problem, I firstly played pawn to f3, allowing g-pawn to capture it. Then I mistakened this by Nxf3. Suddenly, chess.com determined that this is an incorrect solution and the actual solution is exf3. IDK why this happened.

I guess knight takes f3 is another solution as well, why not this possible? Any general ideas or explanations for this puzzle problem? Just to LMK, because my puzzle rating has fallen from 1493 to 1477, after failing two consecutive puzzles that I should've got them right, yeah?

I mean my puzzle rating is just close to 1500, but I haven't reached yet. Since I failed two consecutive puzzles today and lost rating of -25 in both, my rating score has dropped from 1493 to 1468 straightforward. So, I just want you to LMK of this second puzzle problem that I have failed. Anyone who can explain this clearly will reward "Thank you" note as your response.

Pawn needs to take as the knights covering f1 to Queen the pawn i think. I'm not great either but that's what it could be.