Why is Qd5 the best move and not Qg1?

Proud of finding this in one of my rapid games.

What about it?

Before Nb4, Black had a slight advantage, but this move is a blunder.

Why is this checkmate?

What about it?

Why is rook b4 checkmate? If the white king takes the rook, the black queen can’t move because it’s pinned by the white rook.

What's the best play to protect my Knight here?

I did it! I know this sun is riddled with these posts but I never thought this day would come!

Thanks, i hate muscles

Thanks, I hate impatient seeds

Thanks, I hate emoji scissors

Thanks, i Hate the Cube

Thanks, I hate banana skins

Thanks, I hate this bathroom sign