<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<div class="header" style="background: #0f1d2b">
<div class="container">
<div class="row">
<div class="col-xl-4 col-lg-4 d-xl-flex d-lg-flex align-items-center">
<div class="row">
<div class="col-xl-12 col-lg-12 col-6 d-xl-block d-lg-block d-flex align-items-center">
<div class="logo">
</div>
</div>
<div class="d-xl-none d-lg-none d-block col-6">
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent"
aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
<i class="fas fa-bars"></i>
</button>
</div>
</div>
</div>
<div class="col-xl-8 col-lg-8">
<div class="mainmenu">
<nav class="navbar navbar-expand-lg">
<div class="collapse navbar-collapse" id="navbarSupportedContent">
<ul class="navbar-nav mr-auto">
<li class="nav-item">
<a class="nav-link active" href="#">About <span class="sr-only">(current)</span></a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Event</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Gallery</a>
</li>