div#testa {

    width:945px;

    height:117px;

    background-image: url(https://etservice.info/img/heads/giappone/head_es.jpg);

}

@media screen and (max-device-width: 380px) {

    div#testa {
        background-size: contain;
        background-repeat:no-repeat;
        background-position:center;
        background-image: url(https://etservice.info/img/heads/giappone/mobile_es.jpg);

    }
    
    div#testa a {
        display:none
    }
    
}