hi!!
So, im not a professional but I can give you some pointers. You said you're a beginner and your work looks really good, I would say, to answer your first question, I would say pratice them seperate as when you do gesture, the details of the face are some of the last things you need to focus on. I reccomend learning general body structure which includes face, look at anatomy books and images as they'll help you understand anatomical structure (which will help with your figure drawing). I also really reccomend praticing base strutures of the body. with faces you seem to struggle with general structure and youre jumping into details too quickly. try to get overall structures correct before adding details. when doing faces the most important thing in my opinion is eyes and mouth and nose bridge.
i hope this helps a little bit
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