Wordpress儿童主题css崩溃

I'm very confused and need your help! I created Twenty Sixteen child theme and everything was working perfect, the child style was overriding the parent's one. Then suddenly, when I made a little change of the menu in the WP admin, child css stopped being dominant. After this in all child theme I've created, parent style always overrides child css. Here is the code I put into child css.

/*  Theme Name:   Proservice_2016
    Description:  Proservice Theme
    Author:       VB
    Template:     twentysixteen
    Version:      1.0.0
    Tags:         light, dark, two-columns, right-sidebar, responsive-  layout, accessibility-ready
    Text Domain:  proservice
 */

  @import url("../twentysixteen/style.css");

Also in functions.php I inserted the following code

<?php
 function parent_css_theme_style() {
 wp_enqueue_style( 'parent-style',   get_stylesheet_directory_uri().'/style.css' );
 }
add_action( 'wp_enqueue_scripts', 'parent_css_theme_style' );
add_action( 'wp_enqueue_scripts');
?>

Here a working example as I tried it:
functions.php

<?php
add_action( 'wp_enqueue_scripts', 'parent_css_enqueue_styles' );
function parent_css_enqueue_styles() {
    wp_enqueue_style( 'parent-style', get_template_directory_uri() . '/style.css' );
}
?>

All the information you need: https://codex.wordpress.org/Child_Themes