Can the word ''kvar'' be used in this sentence like fortfarande? ''Han skriver kvar brev till mig'' (I have trouble understanding the concept of ''kvar'')
No, you cannot use "kvar" in this context. "Kvar" essentially means "remaining", be it in a temporal way ("det är fortfarande tid kvar", "there is still time left") or a spatial way ("han står fortfarande kvar där", "he is still standing there").
Im a swedish speaker myself so I can't say Im 100 % sure since this is translating to english but if he "still writes", at this point in time still doing something, isnt "is still writing" also valid?
Gave me a wrong answer though. Maybe I didnt pay attention and had another error.
Because that's, to my knowledge, not grammatically correct English. It's either "writes letters" or "writes a/the letter".
In English we often drop the word letters, and just say we are writing to someone, the assumption being that of course we are writing a letter. Does that happen in Swedish also?
It does, though I would not recommend translating it that way on Duolingo; it's best to be precise so the computer knows you understand.
anybody knows about the etymology of "fortfarande"? Google-translating the components it seems to mean "fast" (fort) - "process" (farande), but this does not make much sense as "still" :/.
It's from a verb fortfara which is no longer in use, but which meant to "continue".
fort in this case isn't in the modern meaning of "fast" but in the meaning of e.g. the English cognate "forth".
fara in this case also has an older meaning - that of "proceed".
So it's more like "forth-proceedingly", if you will. Certainly not immediately obvious. :)