You captured the porportions quite accurately from the photograph. Overall, it's a nice beginning for only 20 minutes. What if you thought about making some parts darker and other lighter to give the viewer a better sense of what is the focus of the drawing. Right now, the eyes are clearly the focus. Maybe, having looked at the photo again, if you darkened part of the background. In the photo, the area behind the top of the head is dark and this makes it really pop out.
Just a thought, and bully for you taking the time to sketch. My day was full of Christmas preperations, and I am just now, at 10pm going to wrap presents!