Anyone got any general tips? Mainly for the middlegame, seeing as the endgame is pretty much an unloseable position by that point.

=]

is it a quick mate?

You make some blunders, just checking if your pieces are under threat would help.

Like, on move 13: you could play BE6 and save your pawn. 

Or on move 16 you could play NXE3 and not loose a piece. 

Or, on move 16

After 13...Be6 14. Nxe4 dxe4 I'm still a pawn down no?

And you mean 16...Ne6, which would have been a better move tbh, I think I was too pre-occupied with keeping my pieces forward.

You played the opening quite sanely--unlike your opponent--and by move 13 you had a decisive material advantage, as well as very active pieces. You might look at either 13...Rhg8 or 13...Nc5. They both look much better than the move you chose. For instance, after 13..Rhg8 14.Nxd5 Bf3 15.g3 Ng5, you have a crushing advantage.

16...Nf5 just tosses a piece away. I suspect you just lost concentration here and didn't count attackers and defenders. Or you missed that 18.Bxg6 was with check. Just 16...Ne6 was fine.

It looks to me as if you need to work on your tactical alertness--just like the rest of us. If you had done a simple safety check before making your moves, you would have had an easy win in the middle game

Thanks for the suggestions, guys =]