where did i go wrong?

I played a game against this guy, right, and i felt good about the outcome and my thoughtlines up until a certain point where it all went haywire... I might be blind to

it as it is my own game, but i cant for the life of me see where i f-ed up...

 

So i would apprechiate if someone could analyze the definitive moment of my downfall for me to learn from and perhaps improve my endgame...