bootstrap 4 carousel inside every post of a page [closed]

First, create a custom post type for your portfolio posts:

// Register Custom Post Type
function portfolio_cpt() {

    $labels = array(
        'name'                  => _x( 'Portfolio', 'Post Type General Name', 'text_domain' ),
        'singular_name'         => _x( 'Portfolio', 'Post Type Singular Name', 'text_domain' ),
        'menu_name'             => __( 'Portfolio', 'text_domain' ),
        'name_admin_bar'        => __( 'Portfolio', 'text_domain' ),
        'archives'              => __( 'Item Archives', 'text_domain' ),
        'attributes'            => __( 'Item Attributes', 'text_domain' ),
        'parent_item_colon'     => __( 'Parent Item:', 'text_domain' ),
        'all_items'             => __( 'All Items', 'text_domain' ),
        'add_new_item'          => __( 'Add New Item', 'text_domain' ),
        'add_new'               => __( 'Add New', 'text_domain' ),
        'new_item'              => __( 'New Item', 'text_domain' ),
        'edit_item'             => __( 'Edit Item', 'text_domain' ),
        'update_item'           => __( 'Update Item', 'text_domain' ),
        'view_item'             => __( 'View Item', 'text_domain' ),
        'view_items'            => __( 'View Items', 'text_domain' ),
        'search_items'          => __( 'Search Item', 'text_domain' ),
        'not_found'             => __( 'Not found', 'text_domain' ),
        'not_found_in_trash'    => __( 'Not found in Trash', 'text_domain' ),
        'featured_image'        => __( 'Featured Image', 'text_domain' ),
        'set_featured_image'    => __( 'Set featured image', 'text_domain' ),
        'remove_featured_image' => __( 'Remove featured image', 'text_domain' ),
        'use_featured_image'    => __( 'Use as featured image', 'text_domain' ),
        'insert_into_item'      => __( 'Insert into item', 'text_domain' ),
        'uploaded_to_this_item' => __( 'Uploaded to this item', 'text_domain' ),
        'items_list'            => __( 'Items list', 'text_domain' ),
        'items_list_navigation' => __( 'Items list navigation', 'text_domain' ),
        'filter_items_list'     => __( 'Filter items list', 'text_domain' ),
    );
    $args = array(
        'label'                 => __( 'Portfolio', 'text_domain' ),
        'description'           => __( 'Post Type Description', 'text_domain' ),
        'labels'                => $labels,
        'supports'              => array( 'title', 'editor', 'thumbnail' ),
        'taxonomies'            => array( 'category', 'post_tag' ),
        'hierarchical'          => false,
        'public'                => true,
        'show_ui'               => true,
        'show_in_menu'          => true,
        'menu_position'         => 5,
        'show_in_admin_bar'     => true,
        'show_in_nav_menus'     => true,
        'can_export'            => true,
        'has_archive'           => true,
        'exclude_from_search'   => false,
        'publicly_queryable'    => true,
        'capability_type'       => 'page',
    );
    register_post_type( 'portfolio', $args );

}
add_action( 'init', 'portfolio_cpt', 0 );

Next, duplicate the single.php template file from your theme and rename it to single-portfolio.php. WordPress will automatically load this when visiting a post from your custom post type. You can read more about this, here.

For the gallery functionality, I would use the gallery addon for ACF. This will allow editors to easily upload images and re-order them. You can then output the images within your carousel. When creating your fields within ACF, you can specify the gallery only to appear on the “Portfolio” custom post type.

Here’s an example from ACF showing you how to integrate the gallery with an image slider:

<?php 

$images = get_field('gallery');

if( $images ): ?>
    <div id="slider" class="flexslider">
        <ul class="slides">
            <?php foreach( $images as $image ): ?>
                <li>
                    <img src="https://wordpress.stackexchange.com/questions/327764/<?php echo $image["url']; ?>" alt="https://wordpress.stackexchange.com/questions/327764/<?php echo $image["alt']; ?>" />
                    <p><?php echo $image['caption']; ?></p>
                </li>
            <?php endforeach; ?>
        </ul>
    </div>
    <div id="carousel" class="flexslider">
        <ul class="slides">
            <?php foreach( $images as $image ): ?>
                <li>
                    <img src="https://wordpress.stackexchange.com/questions/327764/<?php echo $image["sizes']['thumbnail']; ?>" alt="https://wordpress.stackexchange.com/questions/327764/<?php echo $image["alt']; ?>" />
                </li>
            <?php endforeach; ?>
        </ul>
    </div>
<?php endif; ?>

If you’d prefer not to use ACF, you could use the WordPress native gallery.