#video-conference {
    width: 100%;
    /*
    position: absolute;
    height: calc(100% - 0);
    */
}

.start-conference {
    position: relative;
    top: -300px;
}

.modal {
    z-index: 9999 !important;
}

@media screen and (max-width: 520px) {
    .start-conference {
        top: -100px;
    }
}