My rating when I was playing is around 2000-2100 ELO so hopefully some of this analysis is helpful.
Trying not to be too overly critical and from a basic perspective I think White had a big upper hand early on with a classic Sicilian style setup. Castling on the alternate queen-side in particular suggests that you're going to be attempting a kingside pawnstorm
From the perspective on Black early on I think it's clear he was suffering from severe under-development. White had only one minor piece under-developed (by move 13) whereas Black still had his Queen underdeveloped plus two minor pieces hemming in his Rook. Also I'd argue Black was applying next to no pressure on the centre at all. I'd argue for a intermediate players it's not okay to concede the centre too early on. Some study of openings would be advantageous here.
A rule of thumb is not to move a piece more than twice in the opening unless it's either a) part of a repertoire or b) required because a piece or there is a severe threat. Either way it's a good rule of thumb to follow.
I would argue that White is in an excellent position by move 14. Both 7... h6?, 11... g5?, 12... Nh5? and 13... a6? are all early mistakes putting Black in a very bad position. Generally it's not advisable to weaken the pawn structure in front of your king (again without good cause) and here there's too much time for White to capitalise and punish Black's weak pawn structure. White missed 14.g4! Nf6 15. f4! gxf4 followed by 16. Bxf4. Threatening to win the pawn on h6 which either forces black to open his Kingside which is obviously not advisable or making a lot of concessions.
Having observed the whole game the fact that Black was allowed to blockup White breaking open the Kingside (with g4) meant that he could buy himself sufficient time to generate counterplay. For me everything after that is a formality since a player who capitalises early on mistakes and follows through with conviction is often the player that ends up winning at the level you're talking about.
I would recommend you check out books by Isaac Lipnitsky if you'd like to understand a bit more about positional play and the likes of Capablance or Nimzowitsch, who are positional masters, to understand what makes a good or bad positional move. This should improve your natural intuition.
Best of luck - I hope that's helpful!
Two books I highly recommend:
Aron Nimzowitsch - My System
Isaac Lipnitsky - Questions of Modern Chess Theory