main menu with one-page + multipage setup?

Hi!

I am trying to create a main menu where the 1st and last menu items links to menu anchors / # / section ID´s on the same page, page 1.
The other menu items links to separate pages on the same website.

If i put in the full url + the section #ID it works but it seems like when I am on the first page that includes the two section ID´s I always seem to have these 2 menu items selected both at the same time in the main menu no matter where I scroll on that page.

If I DO NOT have the full url + the anchors (section) #ID, i.e. just put in #section1 in the menu item, this problem goes away but then the section ID links does not work if I am on another page on the site.

Any ideas how to fix this so that the links work from other pages and also so that I only have the menu item selected that points to where I am scrolling currently at that page ?

Thanks in advance!