how to straighten!?

hmm this could be a problem. you cant really have straight hair naturally if you already have curly hair. Its just unatural to do it.
but we can reduce its fizziness. If you like gel, try to find one with out alcohol. Alcohol dries and firzz the hair out. Use anti frizz serum to make hair less curly. You could also use a blow dryer to straigten hair or a flat iron. A smoothing lotion/straigtning lotion plus blowdryer is a great way to get temporary straight hair.
But the best way to straighten hair is to get it straigten chemically.
there a two ways of doing this. one is getting a relaxer apply to the hair. 2nd is getting the hair rebonded. the later is the best one out their to get bone straight hair. the first one allows some natural waves in your hair.

I also have very thick hair that's alittle curly. I've tried to grow it out but the curls and the poofiness become to much after a few months. If I just deal with it and let it grow, will my hair ever straighten out on its own?

My hair is crazy thick and curly too. I have tried relaxers, which killed my hair, and gel, pomade, and shampoo, and having hair dyed made it worse.

I am starting to grow an afro becuase thats all i can really do, except have it real short.

The only thing that does a decent job is a flat iron, but i stopped using that cuz it dries out my hair too much.