I recommend that you get a human teacher. They can more easily judge these things.
Duo is a computer. It can only match answers against a list of accepted sentences. If there is any difference, it will be rejected, because Duo doesn't actually understand Turkish or English.
Please read this comment from "leighozdemir": You've got the right idea, but in English we would say "strawberries". So, they can add another sentence in data bank. I guess all of us know Duo is a computer. But admins are not computers. By the way, thanks for your recommendation.
These pairs of sentences are also used in the English for Turkish speakers course, so it's best to go with a sentence that is (as far as I know) correct everywhere. Using "strawberry" would sound wrong in many parts of the English-speaking world. Using "strawberries," on the other hand, would be correct everywhere.