Display category in post title?

I want to display the category of each post in the beginning of the title, example: “Category – Subject”, “Movies – Spider Man review!” .

I know a code:

<?php
foreach((get_the_category()) as $category) {
$category_name = $category->cat_name;
}
echo ‘Category ‘ . $category_name . ‘ Movies ‘ . $post->title;
?>

But I always choice two categories, they are “the category” and “it’s parent”
I don’t want to let the Category’s Parent display.
*example: Entertainment – Movies
Entertainment is Movies Parent.