Now, what am I supposed to do in the Orangutan Enclosure?
There's a lot to do there. Firstly, make sure you examine everything for subtle clues. For example, note that the orangutan's feet almost reach the top of the west wall at the pinnacle of his swing. That should give you an idea of your next objective, but you need to get the orangutan off the swing. What do primates like to eat?
Examine the hay, the crate, the hole, the button, the slot and everything else. Experiment with these until you know how to get a banana. You will need at least two bananas in due course.