Wordpress-Custom form in php: how to show results for each submission to the user?

I'm new on Wordpress. I created custom form in php. When user click on submit button, data are sent on my specific table which contains: id(auto increment)/ id_user/display_name/answers (json)/submission_date. I've succeed to create the page which displays all submissions of the user:

<?php

$userid = get_current_user_id();
// On récupère le "display_name" de l'utilisateur
$displayname = um_get_display_name( $userid );
global $wpdb;
$global_steps_submissions = $wpdb->prefix . "global_steps_submissions";
$results = $wpdb->get_results( 
    "SELECT answers 
    FROM $global_steps_submissions 
    WHERE display_name = '$displayname'", ARRAY_A );
$date = $wpdb->get_results( 
    "SELECT submission_date 
    FROM $global_steps_submissions 
    WHERE display_name = '$displayname'", OBJECT );

    ?>
<body>
    <div id="soumissions">
        <?php foreach($date as $d){

            $idSubmission = $wpdb->get_results( 
                "SELECT id FROM $global_steps_submissions 
                WHERE submission_date = '$d->submission_date'", ARRAY_A);
            $idS = $idSubmission[0]["id"];

            echo "<div class='soumission'>
                    <p>Crée le $d->submission_date</p>
                    <a href='.php?param=".$idS."'>Voir les résultats de ce test</a>
                    </div>  </br> ";
        } ?>
        
    </div>
</body>

BUT my problem is: when user click on links, wordpress displays a "page not found". How to add each link as a page which displays results of the specific submission(with id in parameter)?

My page which displays all submissions of the user The page where user is redirect