Help!? what happened to my curly hair?

My hair used to be thick and curly but my hair was damaged so badly from using my flat iorn at 402 degrees everyday that my hair broke off and only the back is curly now and the front is straight I was told from my friend who is a hair stylist that this is most likley why my hair has become thin and not so curly and i really miss my curly hair how can I get it back fast and I've tried to not use any heat but its so hard because I don't want to look like a weirdo with the way my hair is now so how whats a really good heat protectant? and what temperature should I set my styling tools? also how can I get back my thick curly hair please help me thankyou so much!