[HELP] hide sub-menu of horizontal menu

[drabe]

Hi,

I want to disable all my sub-menu except one "Autres Régions", but i really don't know how to do this. I don't know how to target one particular part of my horizontal menu, I tried to target it with the function CSS nth-child(x) but it's doesn't work. I'm new at Prestashop, then i'm lost and I hope someone will be able to help me

 

Url of my site : http://www.creation-site-wordpress.fr/lvdf