Smoking does reduce haur growth and in males it causes thinning and baldness on long term. So better to quit slowly. Regarding dandruff, depending upon severity, do causes hair fall. Ketoconazole based shampoo will help you in reducing dandruff. It is not curable, but twice weekly shampooing will control it properly.
Next Steps
if dandruff is associated with itching and pimples, associated with hair fall, bettter complete few month treatment from nearby dermatologist.
Health Tips
start healthy life, use conditioner, eat dry fruits and increase water intake.