To get you started on answering these questions, let's take a moment to review the definition of "contact zone." According to Mary Louise Pratt, the contact zone is the place where cultures meet. These meetings are often filled with tension as people try to sort out their differences and cope with inequalities even as they forge relationships.
The contact zone idea fits nicely into Robert Louis Stevenson's "The Beach of Falesá," for two cultures are meeting on the island. One one side, there are the natives led by their chiefs. On the other, there are the British traders like the protagonist John Wiltshire and the antagonist Case. Wiltshire especially struggles to understand the customs of the natives even after (and perhaps because) he takes a native wife, Uma. She is under some sort of taboo that Wiltshire has difficulty grasping but that affects him greatly, as the other natives will not trade with him.
Case, who has set up this marriage, already knew about the taboo and therefore uses it to manipulate and harm Wiltshire. Cultures are coming together, and difficulties multiply as they try to understand one another. In the case of Wiltshire and Uma, though, the contact zone leads to success, as they end up with a true marriage.
Now let's brainstorm for a bit about the relationship between the colonizers (here represented by the British traders) and the colonized (the natives). Case is particularly important here, for he clearly views the natives as inferior, and he takes advantage of them, playing on their fears of devils to manipulate them into acting as he wants. By keeping the natives terrified, he can keep them under his control and make a profit off of them.
But Wiltshire cannot stomach this, and not just because Case has manipulated him as well. He destroys Case's fake devil set up in the woods and exposes the man's hoax to the natives, especially to Maea, one of the primary chiefs, who is more than a little suspicious of Case and decides to support Wiltshire. Wiltshire actually ends up in a positive relationship with the natives by the end of the story, and he expects that he will lead a good and profitable life on Falesá. He has no need to manipulate the natives, because he relies on truth and fairness in dealing with them now that they have come to understand each other.