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I think the big thick circle is getting in your way, you only need the guide briefly so I'd make it thinner/lighter or erase it when you start adding features. I would also give yourself more space to work with, by working with a thinner line more zoomed in, (I normally work traditionally so IDK), I'd also recommend looking at a set up tutorial for the software you are using for the type of drawings you are doing, I would find it really difficult to place guidelines and details using the thick, opaque brush you are using right now. 

You've said you are doing 20 minute drawing but I find the class mode a lot more useful, it slowly warms you up into doing longer and longer drawings. 

Keeps going and I hope this helps! x

The characters are all quite expressive, but I think in profile a straiter face line would give a more accurate face shape.