#whatsappButton {
    position: fixed;
    right: 40px;
    bottom: 40px;
    background: url(whatsapp.png) no-repeat;
    display: block;
    width: 50px;
    height: 50px;
    background-size: 100%;
     z-index: 9990;
}
@media (max-width: 768px){
    #whatsappButton {
        bottom: 60px;
    }
}