Endgame troubles!.
Black is Nd6, which simply forces the King to retreat, and allows White to counter Black's advancing Pawn with his own.
This endgame was a theoretical draw at every move. When both sides have equal material and reasonable positions going into an endgame, that's hardly surprising. But you apparently didn't know it was a draw, so... what about 3...Nf5+? - You didn't have to drop that pawn, and your opponent would have opportunities to go wrong (Kd5 or Kc6).
Btw, you should post ENDGAME questions in the ENDGAME forum.

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I have trouble with endgames now. Anything would help. Here is an OTB game I played: