Creating Child Theme functions.php

Hi,

My parent theme name is Grow and I’ve created a child theme named Grow Child.

I’ve executed the steps specified in Child themes guidance.
Now I have my Child theme activated.

The problem is that when I edit the files from the parent and save them in my child folder they don’t overwrite the originals.
I guess, I didn’t customize my functions.php file properly.

Can somebody help in customization? I use this code which is given in the guidance:

<?php
add_action( 'wp_enqueue_scripts', 'my_theme_enqueue_styles' );
function my_theme_enqueue_styles() {
 
    $parent_style = 'parent-style'; // This is 'twentyfifteen-style' for the Twenty Fifteen theme.
 
    wp_enqueue_style( $parent_style, get_template_directory_uri() . '/style.css' );
    wp_enqueue_style( 'child-style',
        get_stylesheet_directory_uri() . '/style.css',
        array( $parent_style ),
        wp_get_theme()->get('Version')
    );
}
?>

Please, tell me where to write what?