I'm a Westerner who's living in Vietnam for several years now. And Duolingo is great help to remember words. Yes there are grazy sentences, but you remember the words. I did an official Vietnamese language course here and i can tell that the way they teach here is very boring. Very difficult to remember words. Duolingo keep up the good work .
no. your sentence would mean "you are the chicken over there."
"đấy" is an adverb of place, indicating a relative spatial position further than "đây". (there vs. here)
"này" is a demonstrative determiner, indicating a relative spatial position close to the speaker, in opposition to "ấy" or "đó" (this vs. that)
ps. be careful with diacritics: bạn, not bàn (which means a table)