Menu issues

Hi – first a big thank you to creating this theme and making it freely available. I’m new to wordpress (this is my first website) so please bear with me if this is a silly question.

Other than the home page my site has 3 primary pages, each of which has 2-4 sub-pages. I’m having issues with navigating these pages, both on a PC/tablet and mobile device. I’d like all of the site’s pages to be accessible from any page, via the main menu.

Here’s the issue – on a PC/tablet, from the home page the menu only links to the sub-pages (not the 3 primary pages). From the sub-pages though, the menu only links to the home page and the 3 primary pages (not any of the sub-pages).

On a mobile device, the menu is replaced with a box with 3 lines in it. From the home page this expand to a full menu, but again this only links to the sub-pages. From the sub-pages the menu doesn’t work at all (it doesn’t expand or show any page options).

I’m very new to this so I’m sure there’s a simple answer – I’d really appreciate if someone could take a quick look and let me know how to fix it.

Thanks in advance
Steve