vinidivici: 19.Bg5 is a good move.
if 19...f6? (better just like the game Qc7!) 20.Qf5
Now all the moves bad for black
A) 20...g6 21.Bxg6 Qc7 (21...fxg5/axb5 22.Qxc7# or 21...hxg6 22.Qxg6+ Kh8 23.Bxf6+ Qxf6 24.Rh5#) 22.Rxb6 hxg6 23.Qxg6+ Qg7 24.Qc2!
A1.24...Qxg5 25.Qxc4+ Kh8 26.Rxd6...1-0
A2.24...fxg5 25.Rxd6 (intending Rg6) Kh8 26.Qxc4...1-0
A3.24...Rbc8 25.Rxd6 Qxg5 26.Rd7! Rf7 27.Rxf Kxf 28.Re1 (threatening Qh7) Qh5 29.Qe4 Rf8 30.d5! Kg7 31.d6...1-0
A4.24...Rbd8 25.Qxc4 Qf7 26.Qxf Rxf 27.Be3...1-0
B)20...h6 21.Bxh6
B1.21...axb5 22.Bxg7 Qe7 23.Qh7+ Kf7 24.Bxf6+ 1-0
B2.21..gxh6 then mate in 2... 1-0
B3.21...Rf7 22.Bg6 Rc7 23.Bg5 axb5 24.Re1 Be5 25.Qh7+ Kf8 26.Rxe5...1-0 (if 22...axb5 23.Bxf7+ Kf8 24.Bxg7+...1-0)
B4.21...Qc7 22.Rxb6! Qxb6 23.Bxg7 f5 24.Qh8+ Kf7 25.Qh7 Bh2+ 26.Kxh2 Qg6 27.Qxg6+ Kxg6 28.Bxf8...1-0
B4.21..f5 22.Bg5 Qc7 23.Rxf5 Rf7 24.Rc5 (threatening Qh7+) ...1-0
There have to be some lines i didnt put here or i missed those. After 19.Bg5, you CANNOT do 19...f6, It brings fatal consequences after Qh5.
What making it hard is there are so many potential moves once you miss it, you could be deprive all the advantages.