Chess Opening Theory/1. d4/1...e5/2. Nf3/2...e4/3. Nfd2

This is the only move that makes sense. You seem to retreat the knight to a safe place and also attack undefended pawn in hope to develop normally. But black has an interesting response - e3 (!?) - they sacrifice their semi-isolated pawn for good. It's forced to either take it or move the knight once again. But every one of them is bad - if you take it you think you just got a free material (even chess engines don't like it), but in exchange you ruin your kingside, your pawn structure,open your king for attacks and block your center pawn. If you move your knight, black just takes pawn on f2 and then you're unable to castle anymore.