"They are not here yet."
Translation:De er ikke her ennå.
"Ennå" is an adverb dealing with time, and may be translated as either "still" or "yet", depending on the context.
"Enda" has several meanings; it can be used to mean "even" (as in "even more/stronger/better), "even if" or "despite" and a few other things. It can also be used in place of "ennå" when dealing with time, but this is a new development and still looks wrong to some.