.request__block {
position: absolute;
content: ' ';
max-width: 450px;
width: 100%;
height: -webkit-calc(100%);
height: calc(100%);
background-image: url(https://klike.net/uploads/posts/2019-01/1547365376_1.jpg);
-webkit-background-size: cover;
background-size: cover;
background-repeat: no-repeat;
background-position: top center;
padding: 15px;
margin: auto;
top: 0; left: 0; bottom: 0; right: 0;
}
.request__bg:after, .request__bg:before
height давать больше 100%, и top -20% request__block по центру .request__bg