Thanks for query,
First of all you stop straightening it.
Second don't use any chemicals like shampoo on it.
sulphate ie selsun
shampoo for your dendruff.
Take vitamin rich diet.avoid junk foods.
Take oral multi vitamin tablet with vitamin E
for at least 6-8 months.it is compulsory.
Apply good coconut oil on scalp
You will get result within 10-12 months.