Disable Mobile Menu

Hi 🙂
I would like to disable the mobile menu (Hamburger) completly. You advised a member here to add the following code to custom CSS.

@media handheld,only screen and (max-width:900px){
#show-nav-menu{display:none !important}
#main-nav { display: inline-block !important; }
}

This wont work on mobile phone and still show the Hamburger menu.
Anything i can do?

Greetings Dean