customization - Issue with navigation bar in child theme

I have created a child theme of the evolve theme. The evolve theme was not edited before localy and was just downloaded from the offical site.

functions.php of child theme:

<?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' );

}
?>

style.css of child theme:

/*
Theme Name:   evolve Child
Theme URI:    [/]
Description:  evolve Child Theme
Author:       Michael
Author URI:   []
Template:     evolve
Version:      1.0.0
License:      GNU General Public License v2 or later
License URI:  .0.html
Tags:         evolve,child
Text Domain:  evolve -child
*/

After activating the child the in the wordpress ui, the arrow of the navigation bar was crashed (please look screenshot):

broken navigation bar in child theme

navigation bar in standard theme

Can you tell me how this could occur and can I somehow fix this issue? I’m very new at wordpress, so I hope the informations in my questions are correct and complete. Please refer if you need more informations.

Thanks a lot!