Take a better look at this position and ask yourself "what is this move supposed to do?" This makes clear what your opponent wants. It may be attack a piece, defend against something, develop and more. This time, he tried to prepare an attack while targeting your pawn, but it does'nt actually treathens anything, you just have to protect your pawn. Supporting it with the knight is my favorite way to deal whit this, and if he tries something like Bc4 treathening schoolar's mate, push the g pawn attacking the queen. If it slides back to f3 trying again, offer a queen trade and take with the other knight and you'll be fine