There's a lot to like in this. I hope you continue to work at this, because it's a good start. Your harmonies are interesting, and your melody has a great nocturnal feel, like a more fluid gnossienne piece, like Satie finding a little of Chopin's suppleness.
In measure 10 you introduce a motif that I wish you would have elaborated for just one more bar. What you have introduces the slightest of tensions before resolving into a quiet, fleeting cadence. If you added one more bar after measure 10 with the same rhythm and with a diminished kind of harmony, it would add more of a sense of release when you temporarily settle down into the f minor chord in measure 12. That's just something that I, personally, would do, though, but I am a bit biased towards dissonance and drama.
I would also consider doing something to elaborate the return to the lyrical theme in the "a tempo" final section. After going through an agitato section and a piu lento section, I was expecting some sort of transformation of the theme--it's like going on a journey but ending up where you started. There are ways to do this with ornamentation--to add color to the familiar theme, or some counterpoint would add more interest by adding more movement and interaction. Then at the very end, I think the return to the opening descending theme would be a little more poignant.
These are all my personal takes, and as such are subjective...they're what I would think about doing if I had composed this. I really enjoyed this and look forward to more from you.
Topic: AJ Long - Prelude in F Minor