main nav menu

Yes. The easy way is to remove the fixed property from the site header. Go to line 2176 and change this

.site-header.light {
background: #fff;
height: 125px;
position: fixed;
top: 0;
}

to this

.site-header.light {
background: #fff;
height: 125px;
position: unset !important;
top: 0;
}