The menu (or menus) can contain links to pages, post categories and links to other pages or files on Internet. Therefore by default the menu must be edited manually. This can be done in the Dashboard->Appearance->Menus.
The pages have a hierarchy that does not automatically propagate into the menu. The hierarchy in the menu must edited manually using a mouse. Drag the menu items up and down to position them in the right order. Drag them left or right to make them sub-items in a menu or vice versa.
It is still a good idea to use a hierarchy of the pages for a good organization/navigation of the pages, even if this hierarchy is not used automatically by the menu.
Making links to posts
This is an example of a link to show posts from a particular category: “Meetings“.
This is an example of a link to show posts that contain a particular tag: “Important”, “COST”. For example in the last case it was enough to enter “/tag/cost/” into the URL field in the link dialog box, WordPress finds the rest.