Translation:He kept the room for six months.
He kept the room for six months.
He had the room for himself for six months.
I believe that "ficar com" means "to keep". If you think about it, "to keep a room" does sort of mean the same thing as "to stay with a room".
It makes sense for me, speaking Australian English, even though it's not the commonest way to say it. He rented it or lived in it for this long.
The best I can find in my dictionaries is "ficar com" to take = comprar (buy) which would give "he took the room for six months, That coincides with amhedh's solution. The other offering of Duolingo, "stayed with the room" is not an expression I have heard in 74 years as an English speaker. The nearest is "He stuck with the room" meaning "he put up with it for want of a better one".
Nor for 74 years. I used "in" here in the sense of "sticking with it" but that was wrong. Yes it does sound like there may have been some reason why he might have moved out, but didn't
This sentence puzzled me, so I guessed "he stayed in the room for six months" and was told it was right :/ Now I have to unlearn it.
It accepted "he stayed in the room for six months." I think this would be a more natural translation although kept could work
First reaction: He stayed in the room for six months o.o?
But then I saw the discussion and somehow I listened correctly to the voice
You wouldn’t use “at” in this context. “In his room” would be fine. Pace Gringoid, “room” with a possessive means a bedroom or hotel room. We also say “He kept to his room.”
But apparently the sense here is not about staying in a room but in maintaining possession of it or the right to use it.