.form-container {
    background-image: 
        linear-gradient(0deg, rgba(9, 42, 30, 0.8) 0%, rgba(9, 42, 30, 0.8) 100%),
        url("https://seu.imgix.net/media/1115925/seugate-1.png?auto=format&h=600");
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
}