You're probably right, but I think this game still has a lot to teach me even well after it is finished. The entire board was used very efficiently by both sides. I would like to continue to examine and slowly work backwards. Maybe I will be able to nail down my losing move. You needn't respond, of course. I will come back and look at more variations in my spare time.
I believe |25.d8 was winning for me.
|20.l5 21.d6
|20.i10 21.k7 22.k11 23.m11 24.m16 25.g9
|20.j8 21.k7 22.k11 23.l10 24.k10 25.m11 26.m16 27.h10 28.i11 29.d6
|20.h9 21.k7 22.k11 23.l10 24.m16 25.h10 26.i11 27.g8 28.g5 29.i9
|20.j9 21.k7 22.k11 23.m11 24.m16 25.g9
|20.h8 21.k7 22.k11 23.l10 24.m16 25.j11
With |20.h10 21.k7 22.k11 23.l10 24.m16 it is different I think, unfortunately I did not analyze |21.e6.
Then I used again some hours for |22.d6, and this time I could analyze until the end and the game we played was one of the variations I studied.
Against |25.d8 I wanted to play 26.e11:
|27.e10 28.g16 29.e17 30.c14 31.d15 32.f9
|27.d9 28.g16 29.e17 30.d13 31.c14 32.f9
|27.h9 28.f9 29.i11 30.h8
|25.d8 26.e11 27.e10 28.g16 29.e17 30.c14 31.d15 32.f9
|25.d8 26.e11 27.d9 28.g16 29.e17 30.d13 31.c14 32.f9
|25.d8 26.e11 27.h9 28.f9 29.i11 30.h8
What about |23.d8 24.e4 25.k3 26.g5 27.k7 28.k11 29.m11 30.m16 31.r13
30.j9 31.f11 32.e4 33.k3 34.g5 35.m11 36.m16 37.r13 or
30.f9 31.l10
What is the plan of white for the next move?
Cause there is a threat on s13 no?
Maybe just 32.s13
|23.d8 24.e4 25.k3 26.g5 27.k7 28.k11 29.m11 30.m16 31.r13 32.s13 33.t14 34.n14 35.s8
and now 36.r11 37.r10 or 36.q12 37.s12
Probably |23.d8 24.e4 25.k3 26.g5 27.k7 28.k11 29.m11 30.m16 31.r13 32.n14
So, how about |23.d8 24.e4 25.k3 26.g5 27.k7 28.k11 29.m11 30.m16 31.r13 32.n14 33.t8 and now for example 34.s13 35.t12 36.o17 37.t16 38.s4 39.q5
Black almost certainly can win either on top or on the bottom, but that's what I have so far.
So it would seem my 21.E6 idea is defeated by 22.D6. I was outplayed relatively early in the game.