"tu n'est pas comprise" means 'you (a girl) are not understood' (although we'd rather say "on ne te comprend pas") - It can also mean "you are not included" (although the formulation is strange as well)
n'est-ce pas means isn't it in French.
the dog has not eaten
I suppose you mean n'est-ce pas ? which means isn't it ?
"n'est pas" means "is not" in English.
Pourquoi pas means 'why not?' in English.
Niqqka
I do not have
It means "not that".
"(ne) sommes-nous pas" means "aren't we ..." in English. This is a question form from "nous ne sommes pas ..." (we are not ...)
" ... n'est pas heureuse " means "... isn't happy" in English. "ne pas heureuse" means "not happy", but is a fragment.
N'est-ce pas means "isn't it" in English.
Bien sûr, pourquoi pas ? means "of course, why not?" in English.