Не работает затемнение главного блока в одном контейнере

.pixel {
  background: url(pexels-pixabay-235725.jpg);
  background-size: cover;
  z-index: 1;
}

.shapka::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 16%;
  opacity: .5;
  z-index: 2;
  background-color: black;
}

.shapka {
  font-family: 'Raleway', sans-serif;
  font-size: 1em;
}

.img_logo {
  z-index: 3;
}

.img_logo_1 {
  height: 100px;
  width: 100px;
}

.but_1 {
  z-index: 3;
}

.a1 {
  text-decoration: none;
  color: white;
}

.a1:hover {
  text-decoration: none;
  color: grey;
}

.main {
  padding-top: 300px;
  padding-bottom: 300px;
}

.blck::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 16%;
  opacity: .0;
  z-index: 2;
  background-color: black;
}

.m_s {
  font-family: 'Raleway', sans-serif;
  font-size: 2.5em;
  color: white;
  z-index: 3;
}

.m_s1 {
  font-family: 'Raleway', sans-serif;
  font-size: 1em;
  color: white;
  z-index: 3;
}

<div class="container-fluid pixel">
  <div class="row shapka">
    <div class="col-lg-2 d-flex justify-content-center d-flex align-items-center img_logo">
      <img class="img_logo_1" src="Logo.png">
    </div>
    <div class="col-lg-2 d-flex justify-content-center d-flex align-items-center but_1">
      <a class="a1">About us</a>
    </div>
    <div class="col-lg-2 d-flex justify-content-center d-flex align-items-center but_1">
      <a class="a1">Spezialization</a>
    </div>
    <div class="col-lg-2 d-flex justify-content-center d-flex align-items-center but_1">
      <a class="a1">Sertifycate</a>
    </div>
    <div class="col-lg-2 d-flex justify-content-center d-flex align-items-center but_1">
      <a class="a1">Contact us</a>
    </div>
    <div class="col-lg-1">
    </div>
  </div>
  <div class="row main d-flex justify-content-center d-flex align-items-center">
    <div class="col-lg-12 d-flex justify-content-center d-flex align-items-center">
      <div class="row blck d-flex justify-content-center d-flex align-items-center">
        <div class="col-lg-4 d-flex justify-content-center d-flex align-items-center m_s">
          XXXXXXXXXX
        </div>
        <div class="col-lg-12 d-flex justify-content-center d-flex align-items-center m_s1">
          XXXXXXXXXXXXXXXXXXXXXXXXX.
        </div>
      </div>
    </div>
  </div>
</div>