This is actually rather nice, and quite impressive for someone learning on their own; nicely done!
Here are the comments I would give if you were my student:
- The most egregious error is in m. 4, with the parallel perfect fifths D/A to E/B between the bass/soprano on beats 2 and 3. This is a definite error in this style that needs to be fixed.
- There's a related error here of the V moving to IV6, which is a retrogression (as opposed to a progression). Your IV–V–IV6 is almost a predominant expansion, but if you really want to expand the IV chord, a better choice on beat 3 would be I64 (which would get you out of the parallel perfect fifths). Maybe try that! (Note: Some might not consider this an error.)
- Your chords are all I, IV, and V. This is not an error, and perhaps this was intentional, but you may try throwing another chord or two in there. Instead of IV, maybe try ii or ii6. Instead of V64, maybe try viio6, which is actually much more common with the 1–2–3 or 3–2–1 bass.
- A very small error is found moving into beat 4 of m. 6. Here, the soprano moves by leap into a B, and the bass moves by step into another B. The rule here is that, if the soprano and bass move by similar motion into a perfect consonance, the soprano must move by step. But here, the soprano and bass both descending into a perfect octave, and the soprano leaps. These are often called "hidden" octaves, but people have different names for them. It's a relatively obscure rule, but it's one I thought I would share; you could easily place a D in the soprano and make this chord a V43 if you like, or make it a viio6 with a few other changes.
Lastly, there are some questions in the comments about a leaping sixth. On beat 4 of m. 4, your bass F♯ leaps down a sixth to A and then immediately back up a sixth to the F♯. Typically, a leap larger than a third will resolve by step in the opposite direction. In other words, your leap down a sixth (which itself is a little large) would almost certainly want to resolve with stepwise ascending motion through B and C♯. But, if you were given these bass pitches, then that's not your error! (But in my opinion, it would be better to just move that A up an octave.) I strongly recommend not just putting an E there, because you'd be left with an illegal six-four chord.