There are two problems (correct me if I'm wrong):

- The first one is to not loose a tempo, or you'll fail capturing the knight on c5.
- The second one and more important to me is that there are only one position where the white queen will be safe and it's on h3. The reason it is not g4 is because of 2...f5 and you loose again a tempo. But the loose of tempo is a minor issue. in fact the critical point is that moving your Queen to h3 will make it a passive piece, and there will be no easy/quick way to activate it again.

After seeing these two points it becomes obvious that exchanging Queens is the best thing to do as you also get the knight right after with almost no compensation for black.

Actually I made a mistake : if 2.Qg4, f5 then 3.Qd4 and now both knight c5 and rook h8 are framed.

I guess the meaning of this is to take advantage of a knight.

After Bxf7 the king just captures the bishop and makes way for the rook. I thought this also.