How can white win after 55. BF2?

#20
Yes 48...Ke3 holds, but 48...Kc1 loses.

So in conclusion, after move 46, with correct play this position is a draw although the engine says -3.4?

#22
Yes, the engine evaluation means nothing if it stays at a stable -3.4.

A high number which doesn't change is no ounce better than a 0.00. A position is only good when it can be improved. The trend is your friend.

1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6 4.Ng5 d5 5.exd5 Na5 6.Bb5+ c6 7.dxc6 bxc6 8.Qf3 Bb7?!
( 8...Be7 = )
9.Ba4 +/- Be7 10.Nc3 O-O 11.O-O?!
( 11.d3 +/- )
11...Nd5 = 12.Nge4 c5?!
( 12...f5 = )
13.Qe2?
( 13.Qf5 += )
13...Nc6?
( 13...Nf4 -+ )
14.Nxd5 += Qxd5 15.Nc3?!
( 15.c3 += )
15...Qd6?!
( 15...Nd4 -/+ )
16.Ne4?
( 16.Re1 = )
16...Qg6?!
( 16...Nd4 -+ )
17.d3?!
( 17.Bxc6!? )
17...Nd4 -+ 18.Qe3 f5 19.Ng3 f4 20.Qxe5 Bd6 21.Qh5 fxg3 22.Qxg6 gxh2+ 23.Kh1 hxg6 24.Be3 Nf5 25.Bb3+ Kh7 26.Rae1 Nxe3 27.fxe3 Rxf1+ 28.Rxf1 g5 29.Be6 g6 30.Rf7+ Kh6 31.Rxb7 Rf8?
( 31...Re8 -+ )
32.Rf7 = Rxf7 33.Bxf7 Kg7 34.Bd5 Kf6?
( 34...g4 = )
35.e4?
( 35.g4 +- )
35...Be5 = 36.c3 a5 37.Bb3 g4 38.Bd1 g3 39.Bf3 Kg5 40.a3 Kf4 41.d4 cxd4 42.cxd4 Bxd4 43.b4 axb4 44.a4 b3 45.Bd1 b2 46.Bc2 Ke3 47.a5 Kd2 48.Bb1 Kc1?
( 48...Kc3 = )
49.Bd3?
( 49.Ba2 +- )
49...b1=B ?
( 49...Kd2 = )
50.Bxb1 +- Kxb1 51.a6 Kc2 52.e5 Kc3 53.e6 Bc5 54.a7 Bxa7 55.e7 1-0

#25
49 Bd3 should be 49 Ba2! +- After 49 Bd3 black can defend 49...Kd2

@tpr, you are right, i missed that, fixed.

@tpr after 49.Kd2 you have 50. Bb1 to defend.

#28
It is a draw then.