Yes, 37...Kc4 was a blunder though I'd need a lot of time to analyse 37...f6. Perhaps Black can draw.Angus French wrote:It looks like Marcus was lucky and White could have won with 40 Ke4.
38 h4 was strong but 40 Kd2 was a terrible blunder. Of course move 40 is often fatal.
As you say, after 40 Ke4 Black is lost. The position is WK e4, Pawns b2, g2. h4 versus Kc4, pawns a6, e6, h7.
I don't see how Black can improve on the main line 40...Kb3 (if 40...Kc5 41 Ke5 or maybe just g4 works) 41 g4 Kb2 42 g5 a5 43 h5 a4 44 g6 hxg6 45 h6! a3 47 h2 a2 48 h8Q+ and the tablebase says White mates in 12.