Blunder analysis please

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Xaiadar

I executed a plan that worked, but afterwards I was shown that this move was a blunder and I would like to know more please!My plan here was to sacrifice the bishop to the pawn, then take the pawn with my knight. On the third move, I used the knight to execute a three way fork at C2 and it worked. I was able to take the opponents queen. It worked exactly the way I had hoped and yet I still received a !! for it. Is it due to the opponent playing poorly and falling into the trap when there was an easy counter? I want to improve, so any help is appreciated!

aegischaidar

1. E4 d4 2.nf3 nc6 3.ng1 nf6 and the mistake is in "3. Ng1", it brings his 'g knight back to his home, but this is blunder not an mistake! [?? Is an blunder!] Like the blunder, mistake is like the "small blunder"