Hi,

Try to use this code snippet

.header-mobile-center .wrapp-header .header-left-side,
.header-mobile-center .mobile-nav-icon {
	display: -webkit-box;
	display: -ms-flexbox;
	display: flex;
}

.header-mobile-center .wrapp-header  .right-column,
.header-mobile-center .wrapp-header .header-left-side{
	-webkit-box-flex: 1;
	-ms-flex: 1 0 0px;
	flex: 1 0 0;
}

body .mobile-nav {
	display: block;
}

Regards