<!DOCTYPE html>
<html lang="ru">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<title>Шукачі</title>
<link rel="stylesheet" href="css/bootstrap.min.css">
<link rel="stylesheet" href="css/jquery.arcticmodal-0.3.css">
<link rel="stylesheet" href="css/slick.css">
<link rel="stylesheet" href="css/slick-theme.css">
<link rel="stylesheet" href="css/main.css">
</head>
<body>
<header class="main-page-header header">
<div class="container">
<div class="row justify-content-between">
<div class="col-lg-3">
<div class="link">
<a href="#" class="img-link">
<img src="img/fb.png" alt="facebook">
</a>
<a href="#" class="img-link">
<img src="img/inst.png" alt="instagram">
</a>
<a href="#" class="img-link">
<img src="img/tg.png" alt="telegram">
</a>
<a href="#" class="img-link">
<img src="img/g.png" alt="google+">
</a>
</div>
</div>
<div class="col-lg-3">
<div class="header-btn">
<a href="#" class="link-ua">
Укр
</a>
<a href="#" class="link-ru">
Рус
</a>
</div>
</div>
</div>
<div class="row">
<div class="col">
<div class=" header-logo">
<p class="seekers__text">
<i>Твій портал про туризм</i>
</p>
</div>
</div>
</div>
</div>
</div>
<div class="container">
<div class="row">
<div class="col">
<div class="navigation">
<nav>
<ul class="main-menu navigation d-flex justify-content-between">
<li class="main-menu__item">
<a href="#">Головна</a>
</li>
<li class="main-menu__item">
<a href="#">Новини</a>
</li>
<li class="main-menu__item">
<a href="#">Думка експертів</a>
</li>
<li class="main-menu__item">
<a href="#">Для навчання</a>
</li>
<li class="main-menu__item">
<a href="#">Моя країна</a>
</li>
<li class="main-menu__item">
<a href="#">Цікавості</a>
</li>
</ul>
</nav>
</div>
</div>
</div>
</div>
</header>
/*----specification----*/
body{
font-family: 'Tahoma', sans-serif;
color: black;
font-size: 18px;
}
h1,h2,h3{
font-family: 'Raleway 800';
text-transform: uppercase;
color: #000;
}
section{
padding: 50px 0;
}
/*----header----*/
.main-page-header{
background: url("../img/22-layers.png") no-repeat center top;
height: 228px;
}
.img-link {
margin-right: 18px;
}
.link{
margin-left: 75px;
}
.link, .header-btn{
margin-bottom: 20px;
padding-top: 20px;
}
.header-btn a{
text-decoration: none;
cursor: pointer;
margin-right: 20px;
color: black;
font-family: 'Raleway-Medium';
text-transform: uppercase;
padding: 10px 15px;
}
.header-btn a:hover{
background-color: #ff9f1c;
border-radius: 3px;
height: inherit;
}
.header-logo__img{
padding-bottom: 77px;
}
.header-logo{
position: relative;
}
.seekers__text{
position: absolute;
color: #000000;
font-size: 24px;
margin-top: 95px;
}
.navigation{
background: #1d7a72;
margin-top: 160px;
}
.main-menu{
align-items: center;
}
.main-menu__item{
font-family: 'FuturaPT-Book';
list-style-type: none;
}
.main-menu__item a{
text-decoration: none;
display: block;
color: #fdfeda;
padding: 20px 20px;
}
.main-menu__item a:hover{
align-items: center;
background: #ff9f1c;
border-radius: 3px;
padding: 20px 20px;
}
<header class="main-page-header header"></header>
.container
библиотеки bootstrap, что и является ограничителем для вашего <nav>