Full screen background image

Hello,

i would like to have a custum image as background in all sites.

I tried this from another post:

#main > .container_wrap {
background-image: url(https://www.everythingisforever.com/cms_assets/full-bg.jpg);
background-position: center center;
background-attachment: fixed;
background-repeat: no-repeat;
-webkit-background-size: cover;
-moz-background-size: cover;
-o-background-size: cover;
background-size: cover;
height: 100%;
width: 100%;
position: fixed;
z-index: 0;
top: 0;
left: 0;
}

But the problem is the image overlays al my text and image boxes (the whole content)

Thanks for helping!