are these sentences correct?

[manminder]

1.If it receives enough rain at the proper time, hay will grow quickly as grass.


2.Despite of the pills which are available, many people still have trouble in sleeping.


3.Anthropologists assert that many of the early American Plains Indians did not engage in planting crops but to hunt, living primarily on buffalo meat.

[Tdol]

2- Despite the pills/I spite of the plls (no 'of' with 'despite')
3- But to hunt- but hunted or but in hunting