The background Image I added to blog made every image transparent

I added this code to design > custom CSS, from a recommendation on another post on how to add background images to all blog posts. 
 

/* Site background image */
body[class*="collection-type-blog"] {
.section-background, .page-section {
    background: transparent !important;
  opacity: 80%
}
& {
   background-image: url(https://static1.squarespace.com/static/600a59513babe51392084795/t/63dd7683ab977736bbd31344/1675458179121/unsplash-image-WsEbnsnKbUE.jpg);
  background-size: 100% 100%;   
  background-repeat: no-repeat;
   background-position: center center;
   background-color: transparent !important;
}}

If I don't add the line that specifies opacity, I don't see my background image, but when I do, even the pictures I add inside the post are now opaque. I just want my background image to be opaque, not the foreground images. Here is my website with some examples. Any one who can help, I'd greatly appreciate it. Thank you!

https://www.electricwellness.com/science/emf-mechanisms-of-action

I think maybe my background images is in front of my texts and other images. But I'm not sure. I tried to specificy z-index:0 but that didnt do anything

Change this line

.section-background, .page-section

to this

.section-background, .page-section, .section-border