Hello,

try adding the following:

@media (min-width: 1025px){

.fullscreen-menu .flexnav li a {
     -webkit-text-stroke: 1px rgba(0,0,0,0.3);
}

.fullscreen-menu nav.open {
    background-color: white !important;
}

.fullscreen-menu .flexnav li:hover a, .fullscreen-menu .flexnav li a.active {
    color: #000;
    -webkit-text-stroke: 1px #000;
}

.light-content #menu-burger span {
    background-color: #000;
}

}

in customizer -> additional CSS

Hello, that should do, you just need to modify the media query the styles apply to

@media (min-width: 1025px)

to accommodate the target screens