Child style.css does'nt work

Hello Everybody !
Sorry for my question ! I'm a beginner in Wordpress and Divi. I have created a child theme but if I added a code, It did'nt work. But If I put the same code in Divi Custom CSS, it works!
Can you give me some leads to fix it ? Thank You very much.
My site: https://10jourspourvoirautrement.org
My child functions.php

PHP:

<?php
function theme_enqueue_styles() {
wp_enqueue_style('divi', get_template_directory_uri() .'/style.css');
}
add_action( 'wp_enqueue_scripts', 'theme_enqueue_styles' );


My child style.css with code for text in 2 and 4 columns that works in Custom CSS but not here
[CSS]
/*
Theme Name: My Divi Child
Theme URI: https://demo.infomaniak.com/preview?t=divi-creative-agency
Description: Divi Theme Child
Author: Luc Fayard
Author URI: https://www.infotekart.com
Template: Divi
Version: 1.0.0
*/
/* ligne d'origine dans Divi Creative Agency
@import url("../Divi/style.css"); */
/*Texte en 2 col*/
@media screen and (min-width: 981px){
.deuxcol
{
-webkit-column-count:2;
/* Opera, Safari, Google Chrome */
-moz-column-count: 2;
/* Firefox */
column-count: 2;
/* Internet Explorer */
}
}
#et-top-navigation .et_pb_button:after {
font-size: 23px;
}
/*fin Texte 2 col*/
/*Texte en 4 col */
@media screen and (min-width: 981px){
.quatrecol
{
-webkit-column-count:4;
/* Opera, Safari, Google Chrome */
-moz-column-count: 4;
/* Firefox */
column-count: 4;
/* Internet Explorer */
}
}
#et-top-navigation .et_pb_button:after {
font-size: 23px;
}
/*fin Texte 4 col*/[/CSS]