Menu drop down not working on mobile device

Hello,
I am using an origami premium child theme (because it was recommended, although I have only created the style.css file with no alterations, all changes have been made through dashboard settings which affect the original files…?…., anyway) and am experiencing the following problem.
While on PC (IE8 and chrome) everything works fine ( Safari doesn’t show the header image!!!…) on my mobile device (iPad) the drop down feature of the menu does not work. To be more specific, it works when I’m logged in but not when I visit the site as an unregistered user. (Safari on iPad does show the header image…?!?!!!) frustrating…
Are there any suggestions?
The URL to my site is https://www.darkwood67.gr
Thank you in advance