Sorry I made a mistake in the diagram, the white bishop is on g1 not c1.
Endgame diagrams.

with the bishop on g1, I like 1. Nf6
The threat is simply Bg1-c5-f8-g7#. Black's only defense is to promote the f-pawn with check. So:
1. Nf6 f3 2. Bc5 f2 3. Bxf2
White still the threat of Bc5-f8-g7# and this time there is nothing black can do about it.

Oops, I totally missed that the knight on f6 would be blocking the check from the promoting pawn on f1. So there is no need for white to go back and take on f2 as I had it. Just 1. Nf6 f3 2. Bc5 f2 3. Bf8 4. f1=Q 5. Bg7#

I agree, for it to be a mate in x puzzle it needs to be forced in that many moves, not just winning easily. Even right at the end could black not play Qb2 and prolong the agony for quite a bit longer? Perhaps as showing a nice combo in a game, but as a puzzle it doesn't quite work.

emtofaan, it doesn't bother you that every single puzzle you've given in this thread has been wrong?

Kh6 looks like a really strong first move for the last puzzle, trapping the king in the corner while white advances his two pawns. Haven't really looked at it too hard but maybe it is mate in 4.

Kh6 Rf6+ Kg4 Rf8 repeats the position, so Kh6 doesn't make progress.
But in the solution line, 5. Qg8# is mate

Well, after reading the comments about all the puzzles being flawed, I didn't look too hard, plugged it into problemiste, It finds 4 different mates in 5, startng with Kg6, or Kh6, or Ng7 or c7
I'll post some endgame diagrams, starting off easy, mate in two: