.scrolldown {
    animation: translate-animation 3s ease-out infinite;
}
    
@keyframes translate-animation {
    0% {
        margin-top: -15px;
        opacity: 0;
    }
    50% {
        margin-top: 10px;
        opacity: 1;
    }
    100% {
        margin-top: 0;
        opacity: 0;
    }
}