Here are some suggestions to fill in the blanks:

1. **hobby**
2. **free**
3. **book**
4. **he**
5. **about**

So the completed text would read:

"My name is Hannah. My (1) **hobby** is reading. I read whenever I have (2) **free** time. I read many kinds of books such as history books, science books, and fantasy books. My favourite (3) **book** is Harry Potter. The story begins when an 11-year-old boy discovers that his parents were wizards and (4) **he** starts learning magic at Hogwarts School. The story is (5) **about** Harry's adventures in..."