Hello, @valentecarlo !
I might say that the one on the left turned out pretty good!
the head in the middle wasn't too bad either except for the few parts.
Corner of the jaw wasn't low enough (traced with magenta) and location of the nose was incorrect because you didn't show enough of how much "forward" it goes.
Same goes for the last one. As it tilts forwards a bit all the sections that show us where the eyes will be more curved and tilt downward too.
With drawing face your horizontal lines should be parallel for each other and vertical lines should be parallel too (well to some degree)
The cutouts that we do on the side of the head (where the ear is located) helps us to determine the head tilt so these vertical and horizontal line will be pretty much a guideline for you for drawing the rest of the head.
And also horizontal sections will follow the curve of the ball that we use initially. (Imagine cutting a tomato, how the line will follow through as you rotate an object)
How to draw head from any angle - Here proko will explain you about it all a little bit better than I do and he also have bunch of other videos about Loomis head that I recommend you to check out and draw with him together
Happy painting and I hope this was helpful!