Thanks for your reply!
I guess you are right on move 12. I still had time to develop and find better squares.
On move 18, your e5, Ne4 combination really made me realize that when I play my games I don't usually pay way too much attention on my opponent's weaker squares (due to a missing bishop). That's one more thing I should note when playing. I was too focused on trying to just keep the structure locked in like that and not letting his bishop develop. And yes, the double rooks would have been quite useless.
I think on move 20 I kind of got impatient as I sort of realized I missed out on my opportunity before and that my double rook plan was not so good. I wanted to try attacking the King-side, but I guess rook and pawn is not such a deadly combination.
As for the endgame, I think I could have won it, I just got way too excited for my K and pawn plan. I remember thinking about like 5 different variations, but I never really considered the possibility of my opponent's pawns advancing.
Okay, previously I asked how I could improve and was told to post some games on where I had problems. Here is one of the games I felt like I built up an advantage towards the middle game but I just couldn't execute it well enough and ended up in a draw. Basically what I'm asking is how I can improve on this sort of thing.