I was in your same situation last may. And now my hair looks a lot better. My curls were almost non existent. It's almost back to the way they used to be (3c)
I started out cutting out all heat styling, for the summer. Lol but I cheated like twice(:
And I used homemade protein and deep conditioning treatments.
For protein, bananas, eggs, and mayonaise are good. Lol but it's gross tho. And I just used evoo, Shea butter, and natural conditioners to deep condition.
Rinsing with apple cider vinegar is good too.
Idk why ppl say heat damage is irreversible, cuz my hair is like 95% back. But the top canopy of my hair is like 3b so it gets damage really easily so my ends are pretty straight.... And I doubt they're coming back. It's takes a while, but you'll get there.

Oh and I just did the aphogee treatment last night, it's really good. I thought it might be too much for my hair, but it actually made it really soft(: