As Jacob Peattie mentioned, you’ve made custom CSS changes in a way that does not impact your theme. To expand a bit more, this is the only place you can make changes that will persist through a theme update or change. All other customizations get wiped.
So if you find you want to make further changes, you can create a child theme. You’ll need access to the server/file system for this.
First create a new folder/directory in wp-content/themes/
You need to add two files to this directory: style.css and functions.php
In the style.css file add the following information:
/*
Theme Name: Edin Child
Template: edin
*/
Those are the only two required things in this file. Note that I have assumed that the “Template” is “edin”; make sure this is actually the parent theme directory name. More info.
Next is the functions.php file, which is a little more involved. Here is where tell your child theme to import information from its parent as well as importing its own style info.
<?php
add_action( 'wp_enqueue_scripts', 'my_theme_enqueue_styles' );
function my_theme_enqueue_styles() {
wp_enqueue_style( 'parent-style', get_template_directory_uri() . '/style.css' ); // get_template_directory_uri() returns the URI of the current parent theme, set in "Template" in your style.css
wp_enqueue_style( 'child-style',
get_stylesheet_directory_uri() . '/style.css',
array( $parent_style ),
wp_get_theme()->get('Version')
); // get_stylesheet_directory_uri() returns the child theme URI
}
?>
Then you’ll have to zip your child theme directory up and upload it via the WP admin (or upload via ftp to /wp-content/, no zipping required), and finally activate the child theme. More info.
You can find more about creating child themes directly from the WordPress theme development docs.