Lovely little piece of music, the instruments sound kind of artificial but I'm guessing you don't have access to 1k$ software so I wouldn't worry about that for now.

I think layering and panning more strings could help fill the soundscape somewhat, reverb might help as well.

As for the piano it's fairly simple, might be because you want it that way but adding some chords and counter melodies spanning across octaves might make it more alive and interesting. Also I'd play around with the velocity on individual notes as well when working with the piano to make it more "real" sounding.

The brass is begging for a friend, I'd add another trumpet that plays roughly the same thing to make it more lively. Perhaps even a trombone or something similar to fill the "bass" void that feels awfully empty at the moment hehe.

Just offering some quick thoughts, I'm bad at expressing and giving critique but hopefully you'll learn or be inspired to improve on an already solid piece.

You definetly need to work harder, but it's not too shabby. Keep at it.