Translation:We go there to the table and sit down on a chair.
We go over to the table and sit down on a chair. - was marked wrong. Does it not sound better? I translated it with one chair, but normally I would translate it with chairs. But here, I am always confused, because I don't know what is expected. Anyway the results are marked wrong. :-)
I've seen this issue about more than one person sitting on a single chair a few times. I have a question. In Hungarian, it is possible to have a number of people wearing coats without using the plural of coat. The sentence is crafted in such a way that it's obvious that everyone has a coat. We see this quite often in other contexts too so that, as soon as you say there are 5 of something or a lot of something, the singular is used for whatever the something is. Are we seeing something similar here? We sit on a chair can be said in English as well in the sense of, this is something that we do, but this introduces a different aspect.