I actually like this a lot, excepting the last 3 measures which to be frank, just sound like a mess of notes with no coherent structure. I think you have a good theme here which could use a lot of developing. Primarily when the viola comes in I was waiting for that to actually go somewhere, but then it abruptly cuts out and back to the cello, and ends about as quickly as it began. I don't know how many one minute "conversations" I've had, and this piece is just begging for some more work to be fully fleshed out. I would say that the structure of this piece seems to favor a string trio (Violin, Viola, Cello) over a string quartet, unless you have a really good reason for the extra violin to be there.