Hello Rijk-Willem!

It is possible, but you would need to use the Developer Tools on Chrome to inspect the related elements on a page then apply custom CSS as appropriate. (Screenshot:  https://cl.ly/28b7e22c964e )

I have initially created the custom CSS for you. You can then extend or adjust it as you want:

#mobile-menu-entity li {
    font-size: 14px;
    font-weight: 700;
    letter-spacing: 0.5px;
}
#mobile-menu-entity li,
.mm-navbar {
    border-color: #fff;
}
.mm-menu.mm-opened a {
    color: #aaa;
    padding-bottom: 0;
}
.mm-menu.mm-opened .current-menu-item a {
    color: #050505;
}

Regards,
Paul

My pleasure! Happy to help! 

Something like this should help:

@media only screen and (max-width: 1150px) {
    .site-menu {
        position: absolute;
        top: 25px;
        right: 15px;
    }
}
@media only screen and (max-width: 400px) {
    
    .site-menu {
        top: 0;
    }
    
    #mobile-menu {
        position: absolute;
        top: 0;
        right: 0;
    }
    
}
.mobile-menu-text {
    display: none;
}
.mm-close::after {
    font-size: 18px;
}

You can apply the code by going to "Appearance > Customize > Additional CSS".

If you would also like to use custom CSS for other elements, I recommend Developer Tools on Chrome or Firebug on Firefox to inspect the elements on the page. Then you will know which CSS selector to adjust.

More info: https://uxbarn.com/inspecting-elements-developer-tools/

My pleasure, Rijk-Willem!