Not having read Part 1, I'm not sure whether "Staggie" is meant to be a proper noun or not. With that in mind, I've made a few suggestions for the first two sentences. This is a long text and very open to interpretation. Therefore, I would recommend scheduling with a teacher to review it together so that you can ensure that the intended meaning isn't lost and to help you learn the most from any corrections.
After a few days, the the staggie began to grow rapidly. - noun
After a few days, Staggie began to grow rapidly. - proper noun
The governor thought of writing a letter .... about Steggie. - You can either leave this space blank or, if you want to include "tell about," you'll need to answer: to whom is the information being told? For example: "... to tell the people about Steggie."