"A strong coffee" is specifically a serving of coffee-- a cup or mug of coffee. "Strong coffee" is just referring to the beverage in general.
So if you asked if someone wanted "a strong coffee," you'd be asking if they wanted a serving/cup/mug of strong coffee. Just "strong coffee" would leave the amount up to context-- we could be talking about a teaspoon of coffee or a hundred cups of coffee.
mizinamo, i really get confused with adjective endings in the absence of articles. In the sentence - wo seid ihr so lange gewesen , why is an e put at the end of the lang, there is no noun?? In another sentence- was sind deine wünsche für das neue jahr? why not wünschen for plural wishes?? And in -sie hat vershiedene schuhe, why is e ending for plural shoes?? Can u help pls???
In the sentence - wo seid ihr so lange gewesen , why is an e put at the end of the lang
It's an adverb here.
so lange is used when a long time is meant.
why not wünschen for plural wishes?
The plural of Wunsch is Wünsche, not wünschen with a small w and an -n at the end.
in -sie hat vershiedene schuhe, why is e ending for plural shoes?
Because -e as in die is the sign of plural accusative.
Since there is no article or other determiner before the adjective to carry this sign, the adjective has to do so (= strong inflection).
If you had this as a listening exercise that would be a possible interpretation. But if the sentence was written you need to note the distinction between Sie ("you", formal) and sie ("they"). Both of those conjugate the verb the same way (wollen). As an aside, "she" is not possible as it conjugates the verb differently (will).