I found this puzzle in a newspaper and I really struggeled with it but eventually got it, and the solution was beautiful. Give it a shot!

Very nice puzzle.

wht if black plays g4 ???

when?? 5..g4? then 6.Be7#

Unfortunately for black, he cannot move his Pawns any further as the white bishop can deliver a devastating checkmate with the move to d8. It is interesting that Lehes says that black has no alternative but to take white's Rook. I disagree. Black can move his Queen to b8 delivering a check. White has three options.

Option 1 - move his Rook to c7, blocking the check and at tthe same time be protected by the bishop. Black's King can now move to g5 and the threat of mate is gone.

Option 2 - move his Pawn to  g3 removing the check and delivering its own check. This will be devastating to white as the Queen will take the pawn and reverse the check. The pawn on h3 is gone after the white King retreats into the corner on h1.

Option 3 - King moves to h8. White loses his Rook with a check by the black Queen when she moves to b1. The white Bishop can be a nuisance there after but not for long

Option 4 - move his bishop to stop the check as it is protected by the rook and threatening capture of the queen.

 Oops. Thanks LearnChess, I didn't see that as an Option.

Nice puzzle.

Yep that's why it wont work but I just realised a way for black to prevent the mate. Black should play 5... Qg1+ instead of 5... Qf4+ and white is forced to promote his pawn to win. Quite a bad puzzle now that i realised that :/ but still a beautiful way to win material :P