Navigation Drop Down Issues

I have been sent from one forum to the next so hoping this is it..

I keep trying to add a drop down menu to my navigation in my header. Unfortunately, the sub pages keep showing up over the main navigation page link so that it cannot be clicked on (If you go to the site and scroll over Our Services, the drop down menu shows up over it), and I can’t seem to figure out how to fix this issue. It is only a problem on the computer. The theme is great on tablets and phones.

Please help.

Thank you

The page I need help with: [log in to see the link]