Why would you respond with a6? Even so, why would you exchange the e pawn for the d pawn?
Furthermore, black is still winning after this, but why the f would you play d4?
a6 was your move that punishes white with ease. It is also stupid internet win now win quick move that you can say you are smart cause you read the internet.
Follow the engine to find out the rest....including black is "winning".
Bc4 is a hilarious blunder that can be punished easily.