Hello,
Below are the CSS codes you required to have to achieve your modification. The first one is for changing main navigation font size, second one is for header, left and right part adjust and the last one is for inner banner height.
.main-navigation a {
font-size: 13px;
}
@media screen and (min-width: 1200px){
.site-header .col-md-4 {
width: 33%;
}
.site-header .col-md-8 {
width: 66%;
}
}
.wrap-inner-banner .page-header .inner-header-wrap {
padding-top: 110px;
padding-bottom: 180px;
}
Note: The 13px, 20%, 80% … are default values. You can change it as per your requirement.
Thanks.