After deactivation of Plugin there are fatal errors

Hi there,

i tried the plugin for learning, but quickly realised, that it is sadly not, what i was searching for.

After deactivation i came across these fatal errors. I could imagine that there is some issues with user-based changes in the database. Is there a simple soulution to change some settings (i.e. custom fields) for a as previous state?

The Errors occur on a Page with a custom Shortcode defined in the functions.php:
https://master.fk12.org/personen/

As well as on a post page (with ?Display Post? Shortcode):
https://master.fk12.org/protest-eine-zukunftspraxis/

Thank you so much for your help. I appreciate it a lot. =)

Here attached the custom Shortcode defined in the functions.php:

function mr_list_users($atts) {
    // Keine shortcode_atts, da dann dynamische Nummer von Attributen m?glich
    $query = new WP_User_Query($atts);
    $results = $query->get_results();

    // Keine Resultate
    if (empty($results)) {
        return;
    }

	
    // Resultate
    ob_start();
    echo '<div class="container" data-ref="container">';
    foreach ($results as $item) {
?>

<div class="mix <?php echo esc_html(strtolower($item->display_name)); ?> 
					<?php echo 'year-';echo esc_html($item->year_started_master); ?> 
					<?php echo 'alumni-'; echo esc_html($item->alumni); ?>">
    <a href="<?php echo get_author_posts_url($item->ID); ?>">
        <div class="hover-container">
			<div class="hover-image"> <?php echo get_avatar($item->user_email, 500); ?></div>
                <div class="hover-overlay">
                    <div class="hover-text">
                        <?php echo esc_html($item->user_description); ?>
                    </div>
                </div>
        </div>
		    </a>
    <div>
		<p>
					<?php echo esc_html($item->display_name); ?>
		</p>
	</div>
</div>

 ? ?<?php
    }
    echo '</div>';
    return ob_get_clean();
}

add_shortcode('list_users', 'mr_list_users');

The page I need help with: [log in to see the link]