White font and white background in mobile menu :o !

Site URL: https://www.virturis.de

Hi there, 

my mobile (or small screen) menu of www.virturis.de is unreadable as my font and logo are both white 😱. Can you help me colouring the background of that mobile interface (e.g. grey)? 

Thanks 🙏

Add to Design > Custom CSS

/* Mobile menu */
body.header--menu-open header#header img {
    filter: brightness(0) invert(0);
}
body.header--menu-open .header-menu-nav-folder-content * {
    color: black !important;
}