Hi there,
That layout is actually created with CSS so you would need to delete the CSS that makes the vertical menu.
Try removing this part:
@media (min-width: 1000px) {
body {
padding: 0 50px 50px;
margin-left: 300px;
}
.site-header {
position: fixed;
left: 0;
top: 0;
width: 300px;
z-index: 300;
height: 100%;
overflow: auto;
overflow-x: hidden;
-webkit-backface-visibility: hidden;
-webkit-overflow-scrolling: touch;
transition: .1s ease;
}
.admin-bar .site-header {
top: 32px;
}
.site-header .main-navigation li {
float: none;
}
}
.inside-header {
display: flex;
flex: 1;
flex-direction: column;
align-items: center;
}
.site-branding,
.site-logo {
order: 1;
}
.header-widget {
order: 3;
}
.nav-float-right .inside-header .main-navigation {
order: 2;
float: none;
margin-top: 30px;
margin-bottom: 50px;
}
.nav-float-right .header-widget {
float: none;
top: auto;
max-width: 100%;
}