"You are drinking my wine."
Translation:Vous buvez mon vin.
French nouns need a "determiner", ie a small word that can be an article (un, une des, le, la les, + contracted articles) or a demonstrative adjective (ce, cet, cette, ces) possessive adjective (mon, ton, son,etc).
My wine = mon vin, determiner "mon" is a possessive adjective (masc. sing)
In English, to mean that an action is in progress at the time you speak, you use the continuous verbal form, ie verb BE + action verb in the gerund form (-ing). o you are drinking means you currently drink
In French, this verbal form does not exist (directly translated “tu es buvant” is incorrect). Therefore, you can translate either “tu bois” or “tu es en train de boire”, where the construction verb être + en train de + infinitive correctly expresses the English continuous form.
That literally means "You are drink my wine", which is grammatically incorrect in English, as it is in French.
French does have a gerund form (equivalent to English "-ing" endings), but that hasn't been taught at this point in Duolingo, and I believe it would be the wrong expression for this sentence.