"The girl is not eating lunch."
Translation:Jenta spiser ikke lunsj.
That's a Duolingo thing, I think. I do the German tree and have the same issues on both mobile and laptop. Sometimes it fails me on simple sentences that I know I pronounce correctly even down to mimicking the intonation of the robo-voice. And then I mumble some multisyllable complication through my lunch and it goes through with all words marked green!
I don't know if there is anything to be done, but I'll look through the discussion on the editing side of Duo.