#start {
    display: block;
    position: fixed;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    background-color: rgba(58, 58, 58, 0.8);
}
div.butemmstart {
    display: block;
    position: absolute;
    width: 20%;
    height: 20%;
    top: 40%;
    left: 40%;
    background-color: white;
    cursor: pointer;
    text-align: center;
}
#MyBox {
    width: 400px;
    position:absolute;
    height: 0px;
    background-color: blueviolet;
    overflow: scroll;
}