Hello @nippon276, and congratulations on completing your first piece! The piece is nice and I enjoyed listening to it!
I also took half of that course in the past (I never finished it, though, so I never composed the final assignment). I remember it was a nice course for starting to compose things and getting the hang of how composing worked.
Since you finished that course, I would recommend you to learn the following:
1) Counterpoint: Particularly in two voices, there are many books that teach two and three voice counterpoint in the style of Bach. For example the book "Counterpoint" by Kent Kennan.
2) 4-voice part writing: I do not know many resources for this. I learned from "Harmony Treatise" by Korsakov, which I highly recommend. Back in the day it was one of the resources that helped me the most to start composing with a little bit more confidence.
These two skills are really practical and t you would be able to apply them to your compositions really soon, specially now that you have the basics grasped from the "Write like Mozart" course.
Regarding the piece, others will be able to give more and better feedback but I will point out a few things I saw and I think might help you:
1. Second Inversion Chords
Measure 2 is a second inversion IV chord. Second inversion chords require, normally, special treatment (many times the bass move by step). The second inversion IV chord is somehow similar to the third inversion ii chord in that the bass note (F) normally moves by step to the E. In this case, it might sound better if you have a D in the bass (first inversion IV) instead of the second inversion IV. You can look for the common treatment given to second inversion chords since there will be information online.
2. Melody and Accompaniment
When you have a clear melody and an accompaniment (like in this case) you do not need to worry too much about the melody creating good voice leading with all the notes of the accompaniment. Focus on creating good counterpoint between the melody and the bass mostly. Then fill in the rest of the accompaniment voices without taking to much into account the melody. In other words, you can focus only on the accompaniment having good voice leading internally and those voices could double the melodic notes.
Of course you can also avoid doubling the melody notes in the accompaniment and there is nothing wrong with that. I just comment this because for a long time I was obsessed with writing perfect voice leading of accompaniment and melody together, when, in real compositions, many times the melody tones are doubled in the accompaniment and the accompaniment has good internal voice leading without too much consideration to the melodic contour (except in the melody-bass case).
3. Melody and chord-tones
I believe in the course they teach about passing notes, arpeggiaturas, etc. Always be aware of those when creating a melody (even if, in the end, you decide to write the melody without following those "rules"). For example, in the m.2 you have a IV chord but the last four notes of the melody in the measure are: A-G-E-D. G and E do not form part of the main notes of the chord (Bb-D-F-A). It is not necessarily wrong so, if you like it, it is perfectly okay as it is, but in this case maybe it would sound better by doing A-G-F-D. That way you use the G as a passing tone and, in addition, you do not sound the leading tone E before the m.3.
Many melodic movements are possible but always be aware of the underlying chord to be sure about your choices.
4. Melodic-Bass Countepoint
As commented before, be specially careful about the counterpoint created between the melody and the bass. For example:
a) m.4~5: You have a main melodic contour of F-F-G-E, with a main bass contour of F-F-F-E. It might sound better if the melody and bass did not coincide at the beginning so many times. Also, since you want to do the F-E movement in the bass, it might be better not having the leading tone E in the melody.
b) m.15: In second and third beats you have the same noes in the bass and in the melody (A-Bb). This is not too bad since you are sounding the C after the A, and also the F in first beat on the bass.
Good Job!