thaaat's just a circle. you're using the hairline right for the part since the lines are supposed to be the edge of the hair source, but it didn't look like you were going for an afro here.

You don't need to do it exactly like me, people's hair parts differently! here, I redid this based on your original post:


This one is, as usual, a bit lazy (especially the highlighting, yikes) BUT! The big thing these help with is where hair starts to drape down, where parts in the hair are, and natural places to slap down mussed up hair bits.
Hope that helps!