style.css

*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
body{
    background-color: #191919;
}
.container{
    width: 100%;
    padding-left: 15px;
    padding-right: 15px;
    margin-left: auto;
    margin-right: auto;
}
.gallery-wrap {
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 10% auto;
}
.gallery {
    width: 900px;
    display: flex;
    overflow-x: scroll;
}
.gallery::-webkit-scrollbar{
    display: none;
}
.gallery div{
    width: 100%;
    display: grid;
    grid-template-columns: auto auto auto;
    grid-gap: 20px;
    padding: 10px;
    flex: none;
}
.gallery div img{
    width: 100%;
    transition: transform 0.3s;
    filter: grayscale(100);
}
.gallery div img:hover{
    transform: scale(1.1);
    filter: grayscale(0);
}
#back-icon, #next-icon{
    width: 40px;
    margin: 20px;
    cursor: pointer;
}

@media(max-width: 578px){
    .container{
        max-width: 720px;
    }
    .gallery {
        width: 580px;
        flex-wrap: nowrap;
    }
    .gallery div{
        grid-template-columns: auto;
    }
}

@media(min-width: 768px){
    .container{
        max-width: 720px;
    }
    .gallery div{
        grid-template-columns: auto;
    }
}

@media(min-width: 992px){
    .container{
        max-width: 960px;
    }
    .gallery div{
        grid-template-columns: auto auto auto;
    }
}

@media (min-width: 1200px){
    .container{
        max-width: 1140px;
    }
}