.header-logo {
    background-color:#10151c;
    background-image: url(https://revistas.unicartagena.edu.co/images/background-header-catalogo.jpg);
    background-size: 100% auto;
    background-position: bottom center;
}
.header-logo:before {
    background: #10151c;
    transform: skewX(-35deg);
    margin-left: -50px;
    width: calc(50% + 70px);
}