Two questions. Firstly, what is "natural improver" and what does it do?

And secondly, I want to make my own pizzas to freeze ahead. Still trying to get away from prepackaged foods. How do I make a simple, and soft base? Also, when the pizzas are covered with topping, how long do you bake them for? (and same for frozen please)

Thank you, I've never made anything with yeast in it before.