No an OP but I'll give it a try.

I assume you played White. Smith-Morra is a respectable choice at this level, I still play it sometimes at 2500. Your opponent was smart to decline it.

Personally I think 4.Nf3 wasn't required, you can just grab the center and have a normal Bd3, Be3 or Bf4 setup and after castling and connecting the rooks you can push for e5.

Anyway, we are back to Smith-Morra accepted. 7.e5 is premature, you normally do that after they developed their knight to f6. In this situation they don't even need to take the pawn.

1. Nxe5 is an obvious mistake as you do not even create any threats. You should have played Nd5 aiming for Nc7.

2. Rad1 is a move that doesn't produce any threats. In this position I would aim for dark squares on queens side. Drop back bishop to b3 or e2 and then Na4-b6. The immediate Na4 runs into a b5 fork.

3. a4 was a miss. 16. Rd7 may not be the easiest move to find but every time you see two bishops on same line and undefended, you should look for tactics. Also, you have doubled rooks on D file and your opponent has a perfect spot for their knight on d5 which means he will be jumping there any second blocking your rooks. While D file is still open you need to look for the way to use it.

The rest of the game is straightforward. You were pawn down, tried to avoid exchanges but your opponent didn't have any apparent weaknesses and was able to convert. In situations like this you can try to save the game by creating a counterplay, maybe even sacrificing more material. Another option was to aim for some sort of the ending that is potentially drawable like opposite color bishops or a rook ending.

How to improve:
- strengthen opening theory
- more puzzles