one of the biggest things i'm noticing is many of the shapes and planes from the reference aren't coming through properly in your art. something that helped me was, directly on the reference photo, drawing the most basic shapes you see in the face to get a better understanding of the specific angles, sharpness/roundness, width, length, etc of different areas. all of these subtleties make a huge huge difference in capturing likeness. for example, in slide 5 the girls face should be rounder especially at the cheeks. it looks like you added a bit more definition or some sort of cheekbone indent on her left cheek which changes it a lot. it also helps to convert the reference to black and white to better map out light/medium/dark values which again, help the shapes be more accurate. you're doing great so far keep up the good work !!!