If your hair is damaged the only way to restore it is to cut it off.
That's because hair is dead.
If you don't want to cut it off all in one go then you need to trim it every 6 weeks. This means you are cutting of the same amount of hair from the ends as it grows. In the mean time use a deep conditioner on it that contains protein a minimum of once a week. (If your hair goes hard you have used it too often.)