How do I create....

[ROUBOS]

OK,
how do I create a menu button (top menu with a name of a section), when clicked to display all the Categories linked to this Section, and then when the Category is selected to display the content items.

I have created a Section named "Projects", which is linked to the top menu with the same name, when clicked it displays the content of the categories in that Section. Not just the categories to choose from...

Hope I'm making sense