As a starting point these are good. But I'd suggest to focus on simpler forms first before going all in into portrait. Cubes, spherical, cylindrical forms, like bottles, fruits, perhaps rectangular eraser etc. Would be helpful to draw them from life, not worrying about shading in the process but trying to capture proportions as close to the subjects as possible. Or if drawing portraits is fun for you, and you want to do them asap, you could watch some from Proko either over here or on YouTube called "How to Draw the Head" there are tons. Another option would be Andrew Loomis's book on the heads but it may be deceptively advanced despite being dubbed for beginners. I like how Proko explains Loomis head constructions, it's simple enough to memorize all the landmarks after a couple tries. Good luck! And I hope you will follow along with the course through the end, I'm sure you'd surprise yourself over the growth you had by the end of it!