Divi子主题拒绝覆盖父CSS - body

Question

if this question is duplicate of some other, i do apologize. But i am not able to find the right answer. I am building some web page. I use Divi theme via WordPress. I've created child theme of Divi theme. I've attached custom style.css via function.php in child theme:

add_action( 'wp_enqueue_scripts', 'enqueue_parent_styles' );
function enqueue_parent_styles() {
wp_enqueue_style( 'parent-style', 
get_template_directory_uri().'/style.css' );
}

But when I want to change some main elements, like body{}, it does not override parent style. Mine actual customization process is:

1. Find which id/class have the element, which i wanna change.
2. Via additional CSS in the theme customize the element with class/id I've found.
3. Hope that it will have the exact behavior I want.

I can't find any good source to learn how this all parent->child customization works and I struggle with basic things. Can you help me, how to easily change many elements of parent's theme? Any help would be nice. Thank you guys!

Edit: There is code from site: site_inspect

And there is code in my css:

body.custom-background {
background-image: url("images/pozadie_B5.png");
background-color: black;
background-repeat: no-repeat;
background-attachment: fixed;
background-position: center -25%;
}

When i place this in Additional CSS in THEME customizer, then it works. But in style.css in my child theme it does not.