Your sonatina has quite a few good features, with interesting floaty melodies (I hear the pentatonic scale, which you seem to like a bit), and some similar phrases between movements, which gives the impression of a larger coherence. I like the first section of the first movement a lot, with interesting phrase lengths and unexpected repetitions of small snippets that are pleasantly surprising. This goes for the final movement as well.
However, as with your other piano piece, the harmony often changes either once or twice a bar constantly for long sections, giving rise to a sort of disenchanting monotony that increases as time goes on (the pesante section for example). This makes your modulations less convincing as well, as many composers, such as Clementi in his six sonatinas, often quicken the rhythmic figures and the harmonic rhythm to more easily effect modulations and add variety. You often try to compensate during transitions by increasing or decreasing the performance speed with rits and accls. (e.g bar 57-62 of the first movement), but I'm afraid they are not entirely successful. The second movement particularly suffers from this, as both the melodic and harmonic rhythms are same-ish throughout. You seem to demand too much out of your transitionary phrases.
Also, you should give more love to writing for the left-hand! It has the role of accompaniment throughout the piece, and the figures often aren't very interesting (e.g alberti bass, chord outlines). While there's nothing wrong with wanting to write homophonically, letting it take a subsidary melody, or adding some contrapuntal texture from time to time would greatly increase the musical interest of the piece by means of contrast.
Hope to hear more from you in the future.