Probably not what you want to hear but the only way to "fix" hair is to cut it off. Then condition it really well, especially at the ends. Trust me, it helps keep the split ends away as your hair is growing.
Also, if you are going to straighten it, I suggest you invest in some sort of heat protectant. It helps to stop your hair from getting fried. Personally, I would not recommend straightening it though. I have pretty curly hair and when it was long, it looked really great. I got a ton of compliments.