What are some of the activities that take place during this festival in things fall apart?

it depends on which festival your talking about, consider revising the question. In the week of Peace, the Festival of the New Harvest, no one is supposed to work, almost like a sabbath day, and "no harsh Word shall be spoken to a neighbor". You're just generally supposed to keep the peace and relax, the oppposite of what Okonkwo, who beat his wife during it and shot at another one, did. There are many other ceremonies and festivals however, so if you're looking for a different ceremony or a more specific one, like i said, you should revise the question.

Hope this helps! :)