What is the best treatment for psoriasis? Mainly in the head. And other parts of the body like elbow and knees

See doctor. You may need to consult a rheumatologist if you suffer from joint symptoms. For psoriasis involving mainly the skin, a dermatologist would be your best bet. There is no one best treatment for all psoriasis sufferers and thus only your own doctor can tell you about the "best treatment" for you.