At first, I do not expect that You criticize all four head drawings.
I want to show the progress of one week of digital drawing.
Maybe You can give me get a bit of general advice.
iPad Pro 12.9
a drawing glove.
and excellent brushes.
I do everyday warming-ups to get a feeling of the brushes and the drawing surface and the pressure of the pencil.
I’m surprised how easily You can achieve likeness if You work with different layers from rough to fine.
But it’s only a beginning.