If you hit the target behind the desk with an arrow, the right room will unlock. Inside you can trade in the bow for the real one that works.
I'm a bit confused by the crab game. I will follow my desired prize, and when it stops I pick that prize, but I will have a random gralat be awarded instead. I picked the crab with the prize, and I grab the gralat from the same exact spot as the prize I tried to pick. I'm not sure why this is happening (two crabs don't end in the same exact spot)