When my hair got damaged after dyeing, I started using castor oil. And indeed, it cured my hair. I also use the ProCabelo hair straightener from https://greathaircurlers.com/best-curling-iron-long-hair/. According to reviews, they do not harm your hair, because their basis is ceramic. Now I can...
Just proper nutrition and sport. I sat on different diets for a long time, and when I stopped, I gained weight. Therefore, I just eat the right food and do not eat sweets.