Hiding a specific menu on mobile

Hello,

I am trying to hide a menu from a website, I was able to hide the mobile menu on desktop, however, for some reason I am unable to hide the desktop menu on mobile.

I have tried this:
@media screen and (max-width: 767px) {
#menu-item-80 {display: none !important;}
}

and I have tried this:
@media screen and (max-width: 767px) {
#site-navigation #menu-item-80 {display: none !important;}
}

and a lot of other options, none seems to be working,

I need to hide the "newsletter" menu and allow the m.newsletter to display on site: http://www.westgalil.org.il

Can you please help?