My hair isn't straight or curly, what should I do?

From my hairline and appx 2 inches back, my hair is very straight, but from there it gets curly. If I flip my hair over and pull the straight part to the side, It is all undefined loose curls. When I leave my hair down, it looks weirs because it is perfectly straight near my face and messily curly in back. What kind of styling products should I use? Does Bumble and Bumble straight work well? I have really thin hair, but I have tons of it. If I pull my hair back into a ponytail, its about 1 inch in diameter.