Child theme style.css is ignored

Hello,

I am using the Optimizer theme and created a child theme to make 2 changes in the style.css. The .single_wrap adjustment works fine, but the page_head is ignored. When I use Inspect Element on Google Chrome I can tell the parent style.css overides the child style.css for this part. Page_head is the title banner on my pages. Anyone know what’s up?

Tom

style.css

/*
 Theme Name:   optimizer_child
 Template:     optimizer
*/

/* =Theme customization starts here
-------------------------------------------------------------- */
.single_wrap {
  margin-left: auto;
  margin-right: auto;
  float: none;
}

.page_head {
  min-height: 100px;
}

functions.php

<?php

add_action( 'wp_enqueue_scripts', 'enqueue_parent_theme_style' );
function enqueue_parent_theme_style() {
    wp_enqueue_style( 'parent-style', get_template_directory_uri().'/style.css' );
}

Website: http://www.gelnagels-gina.be