As for your newest drawing, I think the positioning and angle of the girl on the right is very nice.
I myself have been drawing for a long, long, long, long, long time.
I think anything is particularly wrong with your drawings, but you could try practicing drawing hands. When I was about 15 I cold draw everything quite well besides the hands. Took me about a year to get my hands right. XD A tip is to remember that your fingers are separated into 3. Bend your finger. You'll see what i'm talking about.
Anyways, I look forward to see more of your drawings. You'll grow up to be a very fine artist.
