Most Helpful Girl
I think it’s really good. The only thing that maybe needs a bit of work are the eyes. I’m not sure why but they look a bit off.
Most Helpful Guy
I wouldn't try to improve this part further. If your gonna actually make your own manga, you'll have a lot of drawing to do, and polishing the sketch past this is just going to be time consuming. Leaving it this way would also make your art style more unique, which people seem to like. I would just try doing your ink and color and see if you can/need to improve those.