make a fixed menu

Question

I made a hamburger menu for a site that I want to develop, however my idea is that this menu accompanies the scrolling of the screen and opens perfectly independent of where it is on the site, however I did some tests and always gave some problem, so I just left the burger menu itself with nothing fixed, I was wondering if someone could take a look and explain how to fix this.

HTML

<!-- Inicio do menu !-->
<script>
  function myFunction(x) {
      x.classList.toggle("change");
  }
</script>

<input type="checkbox" id="chec">
<label for="chec">
  <div class="container" onclick="myFunction(this)">
      <div class="bar1"></div>
      <div class="bar2"></div>
      <div class="bar3"></div>
  </div>
</label>
<div class="bg"></div>
<nav id="principal">
  <ul>
      <li><a href="#">Home</a></li>
      <li id="sub10">
          <a href="#">Obras <span>+</span></a>
          <nav id="obras">
              <ul>
                  <li ><a href="#">3D Pavement Art</a></li>
                  <li ><a href="#">Evolution</a></li>
                  <li ><a href="#">The Caves</a></li>
                  <li ><a href="#">Unconditional Love</a></li>
                  <li ><a href="#">The Ark</a></li>
              </ul>
          </nav>
      </li>
      <li><a href="#">FAQ</a></li>
      <li><a href="#">Sobre</a></li>
      <li><a href="#">Contato</a></li>
      <li><a href="#">Estilo das obras</a></li>
  </ul>

CSS

@charset "utf-8";

/* Formatação padrão */
* {
    margin: 0;
    padding: 0;
}

a {
    text-decoration: none;
    color: black;
}

body {
    font-family: "Agency FB", Arial, SansSerif;
    font-size: 1.4em;
    background-color: #F1F1F1;
}

ul {
    list-style: none;
}

/* Inicio do css icone do menu hamburguer */
.container {
    display: inline-block;
    cursor: pointer;
}

.bar1,
.bar2,
.bar3 {
    width: 35px;
    height: 5px;
    background-color: #333;
    margin: 6px 0;
    transition: 0.4s;
}

.change .bar1 {
    -webkit-transform: rotate(-45deg) translate(-9px, 6px);
    transform: rotate(-45deg) translate(-9px, 6px);
    background-color: #ddd;
}

.change .bar2 {
    opacity: 0;
}

.change .bar3 {
    -webkit-transform: rotate(45deg) translate(-8px, -8px);
    transform: rotate(45deg) translate(-8px, -8px);
    background-color: #ddd;
}

/* Fim do css do icone do menu hamburguer */

/* Inicio Menu hamburguer */

#chec {
    display: none;
    /* esconde o checkbox */
}

#chec:checked ~ #principal {
    transform: translateX(100%);
    /* Faz o menu aparecer e reaparecer */
}

#chec:checked ~ .bg {
    display: block;
}



#principal {
    background-color: rgba(110, 110, 110, 0.5);
    /* cor do fundo do menu */
    width: 200px;
    height: 100vh;
    /* unidade base do viewport, pega 100% da pagina */
    left: -200px;
    position: absolute;
    transition: all .4s;
    /* Faz a transição/animação do menu */
}

#obras {
    background-color: rgba(110, 110, 110, 0.5);
    /* cor do fundo do sub-menu */
    /* width: 14%; */
    height: 100vh;
    /* unidade base do viewport, pega 100% da pagina */
    left: -100%;
    transition: all .4s;
    position: relative;
    /* Faz a transição/animação do menu */
}

a {
    display: block;
    padding: 20px 5px;
    color: white;
}

a:hover {
    /* hover do menu */
    background-color: rgb(176, 224, 230);
    color: black;
}

label {
    padding: 5px;
    margin: 10px;
    position: absolute;
    z-index: 1;
}

ul {
    top: 70px;
    position: absolute;
    width: 100%
}

ul li span {
    float: right;
}

.bg {
    width: 100%;
    height: 100vh;
    left: 0;
    top: 0;
    position: fixed;
    background-color: rgba(0, 0, 0, .4);
    display: none;
}

/* Fim Menu hamburguer */

#sub10 #obras {
    top: -70px;
    position: absolute;
    width: 170px;
    pointer-events: none;
}

#sub10:hover #obras {
    left: 100%;
    pointer-events: initial
}

#sub10 {
    overflow: hidden;
    height: 66px;
}

Answer 1

You can go to the CSS formatting of this menu and put the attribute "position: Fixed;". It will pin your Mac on the screen, then, to adjust it to your screen, use the attributes "top: Npx;" or bottom, left and right to set your margin relative to the page (N is the number of pixels that the menu will walk).