How To Change The Layers Of Different Page Elements

Hello, got a question about loading different page elements and how one chooses to be on top of the other. I am currently working on a website where I have a slider on the frontpage and menu items (actually submenu items) that drop down from the top, display behind the slider where they are not accessible to click.

Is there a way to tell the main wordpress menu to load on top or to always be on top of other page elements?

Thanks in advance for your assistance,