.header{
  padding: 80px 10px;
  text-align: center;
  .logo, &__title, &__description{
    opacity: 0;
    animation: fade-in-slow 1s cubic-bezier(0, 0.9, 0.3, 1.2) forwards;
  }
  .logo{
    animation-delay: .3s;
  }
  &__title{
    margin-bottom: 20px;
    animation-delay: .6s;
  }
  &__description{
    color: rgba($white, .6);
    font-size: 2rem;
    animation-delay: .9s;
  }
}

.header{
  padding: 80px 10px;
  text-align: center;
  .logo, &__title, &__description{
    opacity: 0;
    animation: fade-in-slow .5s ease-in forwards;
  }
  .logo{
    animation-delay: .3s;
  }
  &__title{
    margin-bottom: 20px;
    animation-delay: .6s;
  }
  &__description{
    color: rgba($white, .6);
    font-size: 2rem;
    animation-delay: .9s;
  }
}

Change header animation timing function
Change header animation timing function
