Yeah, the mix definitely needs work and unfortunately recording isn’t really my area, although neither is jazz as a composer but as a listener my liking for it has grown a lot over the last year.
I’m sure Kenny will have some good comments too, his jazz stuff is great. I thought the piano melody in the first part was too quiet in comparison with the hi-hats. In fact, throughout I thought that the hi-hats are just way too loud compared to everything else, they’re like the loudest thing, at least on my Sennheiser headphone (which is all I have.) Some of the piano notes are struck too hard, particularly on the first beats of the bar and overall the piano sound thin and weak in the character of the sound. I quite liked the Super Mario kind of sound in the B section if you know what I mean, if not well idk. 
As a composition I did like the melodies and style, but yeah around 2 minutes is where ones attention begins to wander away from the repetitions. Great for a first piece using Cubase though. It will be interesting to hear your pieces as you progress. Great first attempt anyway.