bobjanova, the following are all grammatical English:
he slept after he drank
he slept after he had drunk
he sleeps after he drinks
he sleeps after he has drunk
The first two sentences mean the same and are about the past. The second two sentences mean the same and are about the present.
The question here is which tense to use after the conjunction "after". In contemporary English, there is a distinct preference for using the simple past or simple present tense. However, in classic English (say up till 1900, and perhaps because of the influence of Latin), a perfect tense is often used after "after", in order to reinforce the time sequence: he does Y only after he has done X.
Whether Dutch would permit the present as well as the perfect in the DL sentence here I do not know. I suspect it would.
There is nothing wrong with your English sentence. But it seems to me that it is a translation of the Dutch "Hij slaapt nadat hij drinkt" rather than "Hij slaapt nadat hij heeft gedronken".
Granted, the two sentences mean the same thing. But they are nevertheless different.
I assume both the Dutch sentences I have just mentioned are grammatical. Or wouldn't Dutch say "nadat hij drinkt" instead of "nadat hij heeft gedronken"?
"Nadat" is a subordinating conjunction, used when connecting a subordinate clause to the main clause: "Nadat ik heb ontbijt gegeten, fiets ik naar werk." "After I have eaten breakfast, I bike to work."
"Na" is typically followed by a noun and is not used to separate clauses: "Na het ontbijt, heb ik naar mijn werk gefiets." "After breakfast, I biked to work."
Sara, the Duo translation here is "He sleeps after he has drUnk" -- not "after he has drAnk". So Duo has used the correct participle, and there is nothing wrong with the Duo translation.
Of course your suggestion, "after he has been drinking" is also correct -- for, as we know, Dutch statements can be translated into progressive (-ing) forms as well as directly.
Thank you for your prompt replies. I am enjoying learning with Duo's use of phrases in the place of vocabulary and grammar rules. At the same time, I wonder occasionally if the Dutch translations are what an actual Dutch person would say because the English translations are at times stilted and don't always reflect exactly what I would say. Perhaps some versions of the expressions match more closely what people from England would say? All the same, it is not too hard to figure out the tricks that the program is looking for. At the same time, I wonder if Duo constantly updating. Thank you again.