Load scripts and style with do_action hooks in Wordpress.

Load-script.php

<?php

// Disable auto updates
add_filter('auto_update_plugin', '__return_false');
add_filter('auto_update_theme', '__return_false');

function load_css() {
    // Load bootstrap css
    wp_register_style('bootstrap', get_template_directory_uri() . '/css/bootstrap/bootstrap.min.css', [], false, 'all');
    wp_enqueue_style('bootstrap');

    // Load template css
    wp_register_style('main', get_template_directory_uri() . '/css/main.css', [], false, 'all');
    wp_enqueue_style('main');
}

// Fires when scripts and styles are enqueued.
do_action('wp_enqueue_scripts', 'load_css');

function load_js() {
    // Load only jquery
    // wp_enqueue_script('jquery');

    // Load bootstrap and jquery
    wp_register_script('bootstrap', get_template_directory_uri() . '/js/bootstrap/bootstrap.min.js', ['jquery'], false);
    wp_enqueue_script('bootstrap');
}

// Fires when scripts and styles are enqueued.
add_action('wp_enqueue_scripts', 'load_js');