.js-accordion-content {
  transition: height 0.5s ease;
}

.js-header-bottom-nav {

  transition: max-height 0.4s ease, opacity 0.4s ease;
}

.info-block__background {
width: 69.5rem !important;
    height: auto !important;
    opacity: .5;
}

.info-block__background._big {
  transition: transform 2s ease, opacity 0.3s ease; /* Анимация на transform */
  transform: translateY(20em); /* Изначально на месте */

}

.info-block__background._big.active {
  transform:  translateY(0);/* Приподнимаем элемент на 10px вверх */
}