Growing my hair longer, how to style and how to cut? [Male]?

I have short hair but it is really REALLY thick and gets wavy and the fringe gets curly at the tips.

If i straighten it then it looks good but its still short and im growing it longer to just below shoulder length perhaps just for something new. i sometimes use hair wax to keep it full straight but that only works for my fringe not for the top of my hair because the top of my hair is too thick and curly and if i use enough wax for it to be really spiky then its all greasy so i just leave it down, even if i straighten the top its more straighter but still a very slight wave. since im growing it will it just style itself as it grows? or should i get it cut specifically? also my sides and back are really thick what should i do with my sides? just let it grow out thick then it will get less thick on its own or something?

I appreciate the help =]