Just a pointer: keep the range of the instruments in mind
I'm by no means an expert, but it seems to me that your violin is at the lowest part of the range it can play. Personally I would have either shifted the violin part up 1 octave or used a cello, but it depends on what kind of sound you're after. On a real instrument every part of the range would have a different type of sound (mellow, warm, brittle, eerie, etc), but depending on your samples that might not matter a lot.
Also, when it comes to practicing, it helps to know what an instrument (and its player) can and can't do physically, and how a player would typically interact with the instrument. Stuff like breathing pauses for brass or woodwinds, when to add vibrato, ranges, etc. I'm not great at it myself and definitely need more practice and studying on instruments, their sounds and their behavior, but if you're practicing anyways it might be good to keep it in mind.