To duplicate a page click the three-dot menu for that page in the Navigation menu and select Duplicate.
A menu appears where you can setup your duplicate page. Give the page a name, set the privacy and other settings and click Duplicate.
You can organize pages from the navigation menu too. You just need to click and drag them to the desired position, you also can add subpages by adding a new one or by dropping the page on the parent page. Subpages behave like submenu items in the navigation bar.