Niiiiiceeee, good job! 
I actually do air brushing everyday, my grandfather gave me these art items I could use to make
my art even better. You'll get really good at it, if you want I cant give you some tips:
1: Make sure you draw up close, not far. This makes the paint scatter everywhere.
2: Try adding more layers of paper if you are doing air brushing. That way if you accidentally do a
mistake it won't go through the paper or anything. (Stick the layers on top of each other)
3: I can see in the picture that most of the brown color is fading and you want to make it darker.
Try going slowly when you are making your zigzag, circle or any shape.
Hope this helped, try it! 
Thanks for the tips
I also got my airbrush stuff from my grandpa too.
