Can I mix a site of some "normal" pages with one "One Page"?

Hello,
We are working at a new “normal” site of some pages (homepage plus some more pages):
gewaechshaus-ventilatoren
The navigation menu is left (maybe called side menu?).

Now I want to add sections to the homepage only. Must my homepage set to “Enable One Page Elements” now and the 4 more pages not “One Page”?

Can I “Generate One Page Sections” to the existing homepage?

Than I have to add links to this sections to my left menu. Can I add this links to the existing menu, or must it a new left menu?

If all this is not possible with Highend, is it possible with the plugin “Page scroll to id”?

Many thanks in advance.