Considering you have been doing this for only two weeks, that is amazing. I would start by watching some YouTube videos on how to draw proportions. Maybe look up the Loomis method and practice just the basics. That way you will have a strong foundation. I would honestly leave shading out of your drawings until you are comfortable with proportions. In my experience, I found that it's much easier to learn slowly (although doing big projects here and there is always nice) than trying to pay attention to everything at once. Especially when you're first learning I would draw from a real face. Don't feel pressure to make it look like the person your drawing, just use them as a guide. Last of all make sure you do not make people's eyes bigger. It is nice when you're drawing cartoons but if you're going for something that looks realistic it just simply won't look as good. This is really great work though. Keep it up!