My suggestion is to first ignore the details you notice and focus on observing the overall shape. For example, when drawing the face, start by comparing the boundaries between the features and their relative positions, placing them as accurately as possible. Then keep repeating this process as you move into finer details.
If you’re willing, I recommend studying the Loomis method and basic perspective concepts first. For shading, begin with fundamental tutorials on eggs or spheres. Proko on YouTube has a series of free videos you can learn from.
