black to move (what to move in this situation ) i lost the match after making a bad move , e4

First blitz game

Shouldn't my king be able to take the knight if the pawn is pinned to the king

Double whammy!

My first underpromotion to a knight and the best move! Better than sex

Double whammy!

Proud of this move

Why is my opponents move brilliant? Am i missing something?

Pieces Disappeared?

What about it?

I clicked the back arrow to check back a couple of moves, and when I clicked the forward arrow to go back to the current moves two of the black pieces and one of the white ones disappeared. I couldn’t do anything else and had to close the app. Very frustrating and weird bug.

Mate in 3, black to move. white resigned before I saw it.

Can someone tell me how this will be mate?