don't understand best move


What is the point of putting in a screenshot? Why did you not link the game? Is this some joke?
Also, what did the bishop take on c3? Your comment of "seem to just lose pieces uselessly" suggests that is wasn't a piece, but how should anyone figure that out? No one is clairvoyant here.

Since you're already 2 pieces up, it's best just to sac one back and devastate his pawn structure. It's the simplest way to win. Shortest path to checkmate (that's what engines calculate). Plus a simplification tactic as well.

Also note that with the b and d pawn gone, the c4 bishop turns into an outpost with b5 and becomes an indestructible monster worth 5-6 points.
Now understand best move?

this is my best move https://www.catchapk.com/.
"Since you're already 2 pieces up, it's best just to sac one back"
Aren't you trading a bishop for a knight? You're not sacrificing anything

It's much easier for us to understand your game analysis if you post the game itself instead of a screenshot. To do that, get the PGN of the game through the Share button at the bottom left of the right square. Then paste it by clicking the board icon at the top left of the text box then insert it in Load from PGN.