In French there is no equivalent tense to the present progressive in English. We translate both "Are you drinking milk?" and "Do you drink milk?" into "Bois-tu du lait?". In colloquial French, we sometimes use the expression "en train de + INFINITIVE VERB" to express the idea "progressive" tense. For example, you can translate "Are you drinking milk?" into "Es-tu en train de boire du lait ?"

You have to add a hyphen between the verb and the subject, when the verb comes on first position (best level of language):

e.g. "Bois-tu du lait ?" ("Do you drink milk?)

Do not use a hyphen if the subject comes first (more colloquial):

e.g. "Tu bois du lait" ("You drink milk?")