There are 2 ways to change the page order in the menu.
Let's look at the simplest way. The arrows.
In the "Pages du site Web" module, which is found under the "Contenu" tab, you see all the pages of your site. At the far right of each of the editable pages, you have an iconset. Arrows pointing up or down are used to change the order of pages. Simply click on one of the arrows, and the page will go up or down in the order of the pages.