These sentences are really ridiculous.. "She is that bee" "he is that goat" "there is a bat in the train station". Not any words that you would ever really use in a real conversation, nor do they help anyone understand how to speak the language. I'm a native vietnamese speaker and these are incredibly strange sentences to me.
I'm sure you can teach us vocabulary using "real-world conversations" that will be necessary to know on arrival to Viet Nam. When we arrive in Viet Nam,we may not be able to say, "Hello. We are happy to be in Viet Nam," but we will be able to say, "She is that bee." That will be wonderful and very useful, right?
Before you say "I'm sure...", I would recommend you to get to know some other language courses on Duolingo as well as the making of language course in Incubator.
Now I'm not saying our course is perfect, it's not even good enough and we are still working on improving it, but assuming Duolingo courses to meet your standard of language learning wouldn't help you.
And as a native Vietnamese speaker, I'm sure that you started speaking fully formed, cohesive and useful sentences when you were first learning to speak... If someone just wants to memorize useful phrases, they can find that in many places and shouldn't be using Duolingo. The learning structure of Duolingo is to teach sounds, patterns, and structure in a memorable way that will allow you to expand and grow as you progress.
If you want useful phrases you can learn by rote, use Google translate. If you want to actually learn a language properly from the ground up and not be confused and inundated by interchangeable and limitless nouns, then use Dualingo. I can see the point of these lessons even if others cannot.