Dont take me wrong if I am trying to be not just friendly but honest in a concrete and constructive sense.
Yes the overall appearances of your stringqartet is friendly and even charmiing and inspired in some harmonic colors you gave your thematic development.
Here are a few things which I nevertheless think might be considered perhaps in a honest reflection on your composition:
- What you wrote is obviosly not a classical sonataform, but resembles more a rondo what means a theme alternating with a couple of digressions. It is a problem of this form that it makes an overall development of the movement as a whole quite difficult since it tends to return always back to the same beginning. (That is obviously the reason why you nearly never will find a rondo in a first movement of a classical sonata) ) To avoid the thematic monotony which might be the consequence the classic music has developped concepts like the sonata-rondo, combining characters of the sonataforrm (with exposition, development and reprise) and the repetions and digressions of the rondo. This Idea seem to me useful also if you think about the Form you chose here.
- in some parts of the theme but also in some digressions (for instace very nice beg9inning from ca. 2'30) you use with some charm harmonic means which goes beyond the basic I, IV, V, harmony which are often thought being "classical" (which is defenitly even not for Haydn true in any way) If classical composers stay for notably more than one or two bars in this narrow harmonic structure it often has another extraordinary reason which might be something like a more or less dramatic increasing or decreasing dynamic or situations at the begining or the end of a certain part of the form or the movement as a whole supported by a kind of harmonic stasis. When I listen to your Quartet between 1'28 to 2'11 I think there is a very long concertration on the basic harmonic positions but at least in my ears not enough reason to convince me of the nececitty of 40 seconds harmonic motionlessness..
- again another perhaps simila problem which might have also its reason in the rondoform. The classical musc (as far as I understand it becomes rich from its speaking sequence of different muscal characters. Yes of course is that also the reason why the rondo has been so popular in that period. I would suggest if you again remind a bit more how it is usually done in the classical sonataform you always have a basic contrast of to clearly sometimes even extremly different characters beside one more rhythmic accenuated you always find a more lyrical, singing character. Yes, your theme is a well imaginated melody, but you still might contrast it with something more lyrical to get a more obvious contrast on which you might build up your form.
again dont take me wrong I do not want to deny the serene neoclassical charming attitude we all can listen in your music. I just try to be honest since my personal believe is that this might help you more than just being polite and there for not mentioning what perhaps might help to improve it.