"The girl has several turtles."
Translation:Jenta har flere skilpadder.
Atskillig/adskillig (singular) = a good deal of, considerable, quite a bit of. As an adverb (in singular form) = considerably, a good deal, several. Atskillige/adskillige (plural) = several, quite a few, a good many.
But it is old-fashioned, as far as I'm concerned (could be my dialect influencing), to use it as a mass expression in front of a noun. (I would actually not use it much at all...)
I would use it as a noun on it's own, like answering: Has she got any turtles? Yes, several. Har hun noen skilpadder? Ja, adskillige.
Or I would use it as an adverb to enhance a comparative, adskillig bedre = considerably better.
No, but sort of-ish, yes. Hopefully I've got the nuance right (not a native speaker) but I believe it implies a greater number that what several does. Something like the English "considerable".
You could say, Hun hadde atskillig flere skilpadder: She had a considerable number of turtles! Implying something akin to a lot of turtles; certainly more than would be usual for a turtle-owning girl.
Use kvinna for the woman.
I have had jenta and piken marked correct here.
Probably jenten and pika are also in the correct translations for the girl.
Although in some contexts in English either word (woman or girl) can be used for the same person, Duolingo sometimes requires some extra precision from its learners to convey the main idea (rather than the looser usages we can apply). Please note I do not know the nuances of usage with these Norwegian words, so my comments are not about how strict or loose the Norwegian usage can be.