Menu which includes page links and also sub pages

Hi, been playing with grav for a few days and a simple one page theme.
The menu is set to jump to internal page links , but would like to extend it so if there is a subpage

Front Page Menu
Home | Treatments | Contact Us

On a front page, the treatment link will jump to an internal page marker (parallax scroll) and give a brief intro paragraph, but I also would like to incorporate a drop down sub menu if treatments is hovered over.

When hovered the treatments link to show indvidual treatments which have a link to a page for indepth specification about the subject.

How can I go about achieving something like this ?

Will it allow the user to add a new page and it automatically attach to the menu or will it have to be set up by myself and then just allow them content to edit ?

How does the dropdown function work within grav as standard or by incorporating a droptron to make a better menu system ?

What macro code page commands do I need to be looking at ?

Could it be extended so lets the subpage has an automatic 2nd menu appear with internal page links for quick acces s (not necessary, but was just thinking to make it pretty expandable for a an easy UI which would have mass majority appeal ?

Sorry lots of questions lol !

You might want to take a look at some skeletons menu, like the one in antimatter theme: