Menu problem with a main menu and a submenu

I have a problem which i have hard to solve.

The problem!

I have a main menu that will address categories that I am interested in. But submenus should show the links to texts I have.

The main menu should be at the top belov header The submenu should be on the left side

So when you click on a category in the main menu, the links to the content should appear in the submenu.

I have tried many solution but i am not happy with them i have.

The website should wirk both on and offline.

So do anyone have a great solution.

Below you see how it looks but it is very static!