/* ФОН ДЛЯ .uc-shirina */
.uc-shirina {
  position: relative;
  background-image: url('https://static.tildacdn.com/tild3234-3161-4331-b264-656530323666/34217b3e6be395bbcc0d.png');
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
  background-attachment: fixed; /* Можно заменить на fixed для параллакса */
}

.uc-shirina::before {
  content: "";
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  background: rgba(0, 0, 0, 0.2); /* степень затемнения */
  z-index: 0;
}

/* ФОН ДЛЯ .uc-practica */
.uc-practica {
  position: relative;
  background-image: url('https://static.tildacdn.com/tild3463-3833-4561-a439-336163366361/b059be72b34636f24756.png');
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
  background-attachment: scroll;
}

.uc-practica > * {
  position: relative;
  z-index: 1; /* Контент поверх затемнения */
}