Hey!
Yeh since white willingly gave himself the isolated e-pawn you need to use that against him.
A good rule of thumb is that if your opponent has weak pawns, you want to keep rooks on because it makes it easier to attack them.
Therefore, I'd prefer 20...Rae8, followed by slow tripling of your heavy pieces on the e-file to pressure his pawn.
Where in China are you anyway? I'm up in Jinan in Shandong province
This game I really flunked up, and I want to avoid it next time. I was winning in the beginning of the end(game) by a passing pawn, but then it turned out to be a forced draw because I couldn't threaten to promote on both sides.
So there were two factors I was suspicious of: Was it because I traded off the rooks which made the situation worse? Or that simply I haven't made the best use of my knight and king in the endgame? Thanks!
Anyways, here's the whole game (I will not make any self analyzes because I didn't have the time since this was posted at late night):