Hi Medahmed,

I think you want to change background header menu of homepage 3.

If true, you save this code in the last line style.css file:

.header .main-header.main-header-2 {
    background-color: rgba(170, 170, 170, 0.9); /*COLOR HEX: #aaaaaa*/
}


.header-fixed .main-header.main-header-2 {
    background-color: rgb(170, 170, 170); /*COLOR HEX: #aaaaaa*/
}


.header-fixed .main-header.main-header-2 {
    border-bottom-color: #aaaaaa;
}


.header .main-header.main-header-2 .navigation ul>li>a {
    color: #ffffff;
}

Good luck!