Translation:The Chinese airplane flies back to the city.
Really INTO the city in English? Normaly airports are not in the center of cities.
But why do we have to learn suchlike sentences in two! languages, which doesn't make any sense? To go forward at Duo, it is needed to remember and to use them here. First learning and then trying to kick out suchlike unuseful and/or sentences.
Crazy sentences are sometimes much easier to remember. They stick in your head. So, it can be a good tool to remembering the grammar. Maybe this sentence is not crazy enough. :)
Maybe for children, but I would like to learn useful sentences, like in Italian, English or French. It might be funny to play around, but in which conversation do I need it? We haven't yet learned basic konversation sentences but many crazy stuff. Can it be, that English for Hungarians is more ment for children, than for adults?
Duolingo seems to have a pretty grammar-centric approach: only teach things that can be said with the grammar you have already learned.
This means that on some courses, you don't learn how to say "I have two brothers" or "Would you like a cup of coffee?" until fairly late, when possession and the conditional mood are introduced.
Many language courses have a more conversation-centric approach. You learn sentences that you don't necessarily understand grammatically, but that are more useful in real-life situations.
With Duo, you can't really start speaking until you've finished the whole course -- but you'll know more grammar than someone who just took an A1 course in a language.
Whether that's good or bad depends on the learner and their goals and needs (and learning style).
That seems understandable but, personally, I like the eccentric sentences and grammatical structure centred approach. I'll need to acquire additional vocabulary on my own before I can communicate but the course is giving me the a template to create any sentences I want and a sense of how the language really works.