We can solve loading issue by cache

wordpress-developer-code-review-php.php

<?php
/**
 * This code retrieves course data from an external API and displays it in the user's
 * My Account area. A merchant has noticed that there's a delay when loading the page.
 * 
 * == By using cache ==
 */
public function add_my_courses_section() {
	global $current_user;

	$api_user_id = get_user_meta( current_user->ID, '_external_api_user_id', true );

	if ( !$api_user_id ) {
		return;
	}
	$cache_name   = sanitize_key( md5( 'course_key' . $api_user_id ) );
	$cache_group  = 'course_group';
	// get cache here.
	$courses_data = wp_cache_get( $cache_name, $cache_group );
	if ( empty( $courses_data ) ) {
		$courses  = $this->get_api()->get_courses_assigned_to_user( $api_user_id );
		$sso_link = $this->get_api()->get_sso_link( $api_user_id );
		ob_start();
		?>
		<h2 style="margin-top: 40px;"><?php print __( 'My Courses', 'text-domain' ); ?></h2>
		<table>
			<thead><tr>
				<th><?php echo __( 'Course Code', 'text-domain' ); ?></th>
				<th><?php echo __( 'Course Title', 'text-domain' ); ?></th>
				<th><?php echo __( 'Completion', 'text-domain' ); ?></th>
				<th><?php echo __( 'Date Completed', 'text-domain' ); ?></th>
			</tr></thead>
			<tbody>
			<?php
			foreach( $courses as $course ) :
				?><tr>
				<td><?php echo __( $course['Code'] ); ?></td>
				<td><?php echo __( $course['Name'] ); ?></td>
				<td><?php echo __( $course['PercentageComplete'] ); ?> &#37;</td>
				<td><?php echo __( $course['DateCompleted'] ); ?></td>
			<?php endforeach;
			?>
			</tbody>
		</table>
		<p><a href="<?php echo $sso_link ?>" target="_blank" class="button <?php echo $_GET['active_course']; ?>"><?php echo __( 'Course Login', 'text-domain' ); ?></a></p>
		<?php
		$courses_data = ob_get_clean();
		// set cache here.
		wp_cache_set( $cache_name, $courses_data, $cache_group, 30 * MINUTE_IN_SECONDS );
	}
	echo wp_kses_post( $courses_data );
}