.mainHeader {
    top: 45px;
    right: calc(15px + 4vw);
    z-index: 10;
    position: fixed;
    display: flex;
}

@media(max-width: 768px) {
    .mainHeader {
        top: 10px;
        right: calc(10px + 2vw);
        width: 40px;
        height: 40px;
    }
}