treaty of Waitangi

For homework this week we were asked about what we understand about the treaty of Waitangi and what we are still confused about, well I know that the English wanted the land, but I am still confused about what they wanted the land for. I know that they singed the treaty but I am still confused about how they translated it into Maori. And I know that they changed the flag but why did they have to change the flag when it was so awesome in the first place.