Your menu item text is taken directly from your site's page names. When you change a page name, you can see the menu item text change instantly.
If you have added a link to your menu, such as an anchor or external URL, you can also change the menu item text by the following the steps below.
To change the text on a menu item:
Click Menus & Pages on the left side of the Editor.
Hover over the relevant page/menu link.
Click the Show More icon .
Click Rename .
Type the new page name.