JavaScript files are not registered

I am converting an HTML page to a WordPress theme for a customer, and everything was going fine until I got to the JavaScript part.

I can get the css files to work just fine by using

   wp_register_style('header', get_template_directory_uri() . '/css/header.css', array(), 1, 'all');
    wp_enqueue_style('header');

I have tried to add the JS files, but for some reason they are not registered when I test the page. What have I missed?

function shapeSpace_include_custom_jquery() {

	wp_deregister_script('jquery');
	wp_enqueue_script('jquery', 'https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js', array(), null, true);

}
add_action('wp_enqueue_scripts', 'shapeSpace_include_custom_jquery');

function load_javascript() {
    
    wp_register_script('script2', get_template_directory_uri() . '/js/script2.js', array(), 1, 1, 1);
    wp_enqueue_script('script2');
    wp_register_script('script3', get_template_directory_uri() . '/js/script3.js', array(), 1, 1, 1);
    wp_enqueue_script('script3');
    wp_register_script('navigation', get_template_directory_uri() . '/js/navigation_script.js', array(), 1, 1, 1);
    wp_enqueue_script('navigation');
    wp_register_script('scroll', get_template_directory_uri() . '/js/scroll.js', array(), 1, 1, 1);
    wp_enqueue_script('scroll');

}