Looking for some advice

I wrote a short piece and would like to hear what could be done better or sounds odd. I am neither experienced in composing nor am I exceptionally well educated in any music theory. My musical background is some years of playing the Cello and the flute. What I am already aware of is the fact that it's all written in C-major which I should change. However, I am not good at this so I kept it as it is.

You find the score here.