Responsive menu vanishes behind plugin img

Hi,

I hope this is the right place to ask – I wasn’t sure if I needed to change something in the theme to fix this, or if the problem is with the plugin.

In mobile view, the drop down menu vanishes behind the slider plugin image I have on my static front page, making the menu unusable.

I’m not great at coding – I rely heavily on Firebug, Google & trial and error, so I’m stumped as to how to fix this without removing the slider altogether.

Even if anyone can narrow down whether this is a plugin issue or a theme issue I need to resolve, that would be great!

Many thanks

website in question: http://www.flapperfortunes.co.uk (in mobile view)