Making a sub menu drop down with css or otherwise

Hello,

I am currently making a theme am trying to use CSS to make a sub-menu of a wordpress menu to drop down on hovering over the parent li.

I’ve got it to work but it’s displaying horizontally and I need it to drop down vertically:

https://www.berryconcept.co.uk/sandbox/ (at the top, the parent being ‘Solutions)

The css for the whole menu is as follows:

[CSS moderated as per the Forum Rules. Please just post a link to your site.]

Any help would really be appreciated, thanks ??