When I get up in the morning after 7/8 hours sleep I do not feel fresh and mouth becomes bitter why?

The bad taste is usually a symptom of B vitamin deficiency. There are between 13 and 17 B vitamins, depending on who does the counting, and some of them can pretend to be others, and the science is still getting started, so chemistry and symptoms are not well understood. You just have to read a few books about nutrition so you know how to eat right.