My hair is totally vanishing so watcan I do to stop that,I have a little bit of dandruff problem

You could try the hair formula 37 vitamins but no guarantee it will help
Some vitamins for hair which the formula 37 should contain are:
Folic Acid 800mcg, Biotin 200mcg, Pantothenic Acid 200mg, vitamin E, Zinc 30mg, Manganese 10mg, Choline 1000mg, Inositol 250mg, Para Amino Benzoic Acid (PABA)60mg

Faster hair growth vitamins, shampoo

You can also try a PH balanced shampoo. Good quality brand tea tree shampoos are PH balanced

Unfortunately, using a dandruff shampoo or any shampoo will not prevent your hair from falling out. There many factors that can cause the hair to shed or fall out such as heredity, stress, medications, deficient diet, iron deficiency, ringworm or chemicals in hair care products. I recommend that you see a doctor. A doctor can determine the cause of your symptom and prescribed the appropriate treatment.