The Danish requires sharp, attacking play by White. After 5 ... Bb4, you should play 6 e5! d5, 7 exf6 dxc4, 8 Qxd8+ Kxd8, 9 fxg7
7 Bxf7+! Kxf7, 8 Qd5+ wins back a pawn and strands Black's King.
9 Bd2 is too passive. 9 Nd5! is better.
13 Qf3 is a waste of a tempo; there's no reason to move the Queen. It also blocks the f-pawn. 13 f4! presses the attack.
After 16 ... Qg5, there's no way to avoid trading Queens without losing material. At that point, your attack is more or less finished.
Going back a half-move, 16 f4! gives Black problems, as it threatens f5 and also keeps Black's Queen out of g5. Black has no good way to counter f5 and practically has to give up a piece to stop White.
This is a game where I ended up playing the half-danish. I thought that I played fairly well until I blundered away a rook for a bishop (as I explain in the notes). Then I blunder a second time by not noticing that his rook is free for the taking ... terrible play on both parts. I end up drawing the game because he doesn't notice that I can ... What I'm wondering, is if there is something that I can do better instead of trading queens? Or something that I can do to exploit my attack right around then?