Force mobile menu on certain page [SiteOrigin Corp Theme]

Dear all,
I use SiteOrigin Corp in a website, for a page I need to use the space usually for the menu for an input form, so my idea was to force the menu in “mobile mode” also for desktop viewport, but I have some trouble with media queries.

In my page I put

function modifica_css_menu () { ?>
                                                               <style type="text/css">
			                                        #mobile-menu-button{
								display: block !important;
								}
								.main-navigation>div{
								display: none !important;
								}
								</style> <?
                                                            }
                            add_action('wp_head','modifica_css_menu',1000);

but I have a problem with the media query, which uses “!important”: how I can disable it?

@media (min-width: 769px)
#masthead #mobile-navigation {
    display: none !important;