Hou to fixe header and menu on mobile mode - menu

Question

I'm trying to pin the header and menu to the top of the page. In pc mode and tablet mode it works, but when I enter mobile mode it stops working.
When I scroll down the menu is not fixed. This only happens in mobile mode.
I've tried to edit the css code in several different ways, but I'm not able to.
HTML code:
<header class="header container-header full-width<?php echo $stickyHeader ? ' ' . $stickyHeader : ''; ?>">
<nav class="navbar">
<div id="logo"><img src="logo.svg"> </div>
<a href="#" class="toggle-button">
<span class="bar"></span>
<span class="bar"></span>
<span class="bar"></span>
</a>
<div class="navbar-links">
<ul>
<li><a href="#sobre_md" >Sobre</a></li>
<li>Oferta</li>
<li>Implementação</li>
<li>Segurança</li>
<li>FAQ</li>
<li>Imprensa</li>
</ul>
</div>
</nav>
</header>
<script>
const toggleButton = document.getElementsByClassName('toggle-button')[0]
const navbarLinks = document.getElementsByClassName('navbar-links')[0]
const links = navbarLinks.querySelectorAll("a")
toggleButton.addEventListener('click', () => {
navbarLinks.classList.toggle('active')
});
for(let link of links){
link.addEventListener('click', () => {
navbarLinks.classList.toggle('active')
});
}
</script>
.grid-child.container-component {
grid-column: full-start/full-end !important;
}
* {
box-sizing: border-box;
margin: 0;
padding: 0;
}
body {
margin: 0;
padding: 0;
position: relative;
}
.navbar {
margin: 0;
padding: 0;
display: flex;
position: relative;
justify-content: space-between;
align-items: center;
color: white;
background-color: #5aaddd;
}
#logo{
height: 60px;
width: 60px;
}
#logo img{
margin-left: 30%;
height: 100%;
display: flex;
padding: 0.5rem;
padding-top: 10px;
}
.brand-title {
font-size: 1.5rem;
margin: .5rem;
}
.navbar-links {
height: 100%;
}
.navbar-links ul {
display: flex;
margin: 0;
padding: 0;
}
.navbar-links li {
list-style: none;
}
.navbar-links li a {
display: block;
text-decoration: none;
color: white;
padding: 1rem;
}
.navbar-links li:hover {
background-color: #555;
}
.toggle-button {
position: absolute;
top: .75rem;
right: 1rem;
display: none;
flex-direction: column;
justify-content: space-between;
width: 30px;
height: 21px;
}
.toggle-button .bar {
height: 3px;
width: 100%;
background-color: white;
border-radius: 10px;
}
#media (max-width: 800px) {
.navbar {
flex-direction: column;
align-items: flex-start;
}
.toggle-button {
display: flex;
}
.navbar-links {
display: none;
width: 100%;
}
.navbar-links ul {
width: 100%;
flex-direction: column;
}
.navbar-links ul li {
text-align: center;
}
.navbar-links ul li a {
padding: .5rem 1rem;
}
.navbar-links.active {
display: flex;
}
}
#button {
display: inline-block;
background-color: #DEDB45;
width: 50px;
height: 50px;
text-align: center;
border-radius: 4px;
position: fixed;
bottom: 30px;
right: 30px;
transition: background-color .3s,
opacity .5s, visibility .5s;
opacity: 0;
visibility: hidden;
z-index: 1000;
}
#button::after {
content: "\f077";
font-family: FontAwesome;
font-weight: normal;
font-style: normal;
font-size: 2em;
line-height: 50px;
color: #fff;
}
#button:hover {
cursor: pointer;
background-color: #333;
}
#button:active {
background-color: #555;
}
#button.show {
opacity: 1;
visibility: visible;
}