You can structure your Google Doc with the 'document outline' feature. The outline detects and lists headings from your text to help organise your Google Doc.
In order to use the 'document outline' feature, the first step is to use some of the different text headings within your doc.
Highlight the text you wish to change the heading for
Click on the dropdown arrow beside Normal text
Choose the heading type you require
Then you can click the Show document outline icon (to the left or your doc) and navigate your way easily around your Google Doc