How do I keep my curls in?

malibu

My hair is quite thick so whenever I put it in braids it will straighten not even an hour later, same with when I curl it with heat. Nothing works, not even spray!! Do you have any advice?

By the way, I’m trying to impress a certain someone tomorrow and I have no idea what to do with my hair. Share your favourite pretty hairstyles ! (I have shoulder length hair.)