Use the Page Setting functionalities to Hide or Un-Hide your pages from the Menu.

1. Click the Pages link on the top menu or the Plus + button on the page tabs bar to open the Pages & Navigation window. 

2. Hover over the pages list and click the Page Setting icon.

3. The Page Settings window will open: 

4. Check or Uncheck the box: Display Page in Menu 

If the box is checked: the page will display in your menu
If the box is not checked: the page will be hidden from your menu
(Hidden pages are still published, to set a page not to publish, use the "Page Visibility" setting)

5. Click OK to preserve your work.