"furniture" in English is a mass noun and uncountable.
It seems that in Hungarian, bútor is a count noun, equivalent to what would be "one piece of furniture" in English, and in the plural equivalent to (individual) "pieces of furniture" or, more generally (collective) "furniture".
two "corrects" solutions are given: 1. who is sitting down onto the furniture, and 2. who sits on the furniture. I see a problem in both cases. 1. le, is missing in the hungarian sentence. 2. "ra" is not the right suffix (maybe "butorokon"?), as I understand "ra" indicates a motion.