.position-container {
position: relative;
}
.position-container:after {
content : "";
display: block;
position: absolute;
top: 0;
left: 0;
background-image: url(https://hsto.org/webt/5b/ac/ff/5bacff616663f822951184.jpeg);
width: 100%;
height: 100%;
opacity : 1;
z-index: -1;
}
.header_main__logo
display: flex
background-color: red
width: 50%
height: 100%
justify-content: flex-end заменить на justify-content: center
div {
height: 100vh;
background-image: url('http://i.imgur.com/X1iIDmp.jpg');
background-position: center;
background-size: 2600px auto;
}