"She drinks white wine."
Translation:Hon dricker vitt vin.
When I first wrote that comment, we were in beta and typo handling was pretty absurd – han and hon were counted as typos for one another to take just one example – but that's how Duo does with courses in beta, so that users don't risk getting frustrated because of all the errors, missing correct translations etc that can sometimes be left at such an early stage. But these days, typo handling is more or less reasonable. (except for dictation exercises, but that's a different story).
What you're talking about is a more general thing about how Duo works. They tend to give you mostly translation exercises from the target language so that it can indeed be easy to go through courses without learning too much. I'm currently trying to brush up my Spanish and I find the Spanish for English course isn't all that helpful. Luckily, I can resort to the English for Spanish course and get some more challenging exercises, but unfortunately we can't offer you anything like that for Swedish. Personally I wish they would let users customize lessons for themselves, but tbh I don't think that will ever happen.
My gut feeling is that "vitt vin" is much more common than "vitvin", but that "rödvin" is about equally or more common than "rött vin".
"Rosévin" is only compound and "mousserande vin" (sparkling) only separate.
If you order in a bar or similar, you often just say "ett glas vitt" etc, without "vin".
Yes, Duo has improved this a lot since we discussed this here a month ago. As far as I know, the handling of typos is pretty much OK now (it was ridiculously lenient before, counting hon and han as typos for each other, for instance).
75-80% of all words are en gender, and there are some tendencies like living things are usually common gender (with many exceptions like ett barn, ett lejon) and some endings are always a certain gender. Nouns with the ending -ing for instance are always common gender. (not the word ett ting, 'a thing', but it's not an ending there).