.nm-page-wrap {
 background-image: url(https://tzwrtzakas.gr/wp-content/plugins/responsive-full-background-image/images/t-bg-1.jpg);
 background-repeat: no-repeat;
 background-position: center; 
 -webkit-background-size: cover; 
 -moz-background-size: cover; 
 -o-background-size: cover; 
 background-size: cover; 
}