"I am not cheerful, even though I am drinking wine."
Translation:Nie jestem wesoła, chociaż piję wino.
Is there a good time to use 'choć' or 'chociaż'? Or are they interchangable?
Why can I use wesoły and also wesoła. Is not the verv być supposed to be with instrumental case?
Yes, if there is a noun phrase coming after it. If it's just an adjective, it stays in Nominative. You can check here, Part 3: https://www.duolingo.com/comment/16373167
Not sure if this is also a part of the question, but "wesoły" will be what a man will say and "wesoła" what a woman will say. Adjectives need to match the gender, in this case the gender of the speaker.
This is a question that I find more and more often. The problem is, that you treat the construction of Present Continous too literally. If you had Present Simple, it would be clear: "drink" = "piję", no place for doubt. "am drinking" is just a grammatical construction. It doesn't really add another verb (to be) to the sentence. Not in Polish, definitely. Present Simple and Present Continous are translated the same way in 99% of the cases. Your sentence sounds kinda like "... although I am drink wine" It just doesn't make sense, because you added an additional verb to it.
Whenever we place „nie” before an adjective or an adverb we write them as a one word. Hence:
a) Nie jestem wesoły b) Jestem niewesoły
How can we find out the "woman gender" (wesoła) here from English question? Please explain.
You absolutely can't, the masculine and feminine versions are equally correct.