Submenu Stay Open On Menu Click Isn't Working Correct

I have a menu with some items containing a submenu. The submenu's should open when a parent is clicked and contains submenu's, and when traveling to another page (from the item clicked, for example a parent of submenu item), the submenu should remain active and visible.

When I click on a parent (at the moment the hrefs contain no links just #), the submenu opens. But when I click another main item, the submenu of the previous parent remain visible, and the submenu of the parent just clicked is also visible, while I only want the submenu of the parent clicked to be visible or when parent with no submenu the submenu should be invisible.

So, here is the code I have so far:

Code:

The javascript:

Code:

And the css:

Code: