[Grace Themes]

Hi Holger,

To change the background color of menubar in mobile devices
Go to Appearance -> Theme Options -> Basic Settings -> Background Colors -> Select background color for toggle menu

To change the menu background color in mobile version
Go to Appearance -> Editor -> style.css file
add below css code and change the color code as per your need.

@media screen and (max-width:767px) 
{
.header-nav ul li { background-color:#000000 !important; }
}

Second issue: Please send your website URL and some screenshot where the problem is getting so we can check and assist you.

Regards
Grace Themes