How to prevent excess hair loss & dandruff?

please suggest me a method nto prevent this permanent.

is it really dandruff or just dry scalp,, dandruff is big yellow scales and smells,, white flaky stuff is just dry scalp, so moisture shampoo or coconut oil into the scalp is good ,, if it is really dandruff i would consult a doctor, as most of these on the shelf shampoos would do more harm than good to your hair,,,,,,, as for hair loss, not a lot you can do,, you will lose more hair than normal several times a year, this is down to your hair cycle,,,,,, constant extreme hair loss needs a doctors knowledge..as it could be down to hormones or a type of alopecia