Redirect page after x seconds after filling out sendemail.php form

Hi,

I've tried to redirect my page after three seconds to a "thank you" page.
I've tried with header and javascript but I don't do it right.
Can you help me with this?
How can I do this?
Could be a new feature/element in your "canvas package".

Here is the page that should be redirected to a thank you page in 3 seconds: https://www.maximgrimonprez.be/contacteer-schrijnwerker-maxim-grimonprez.html

Thanks a lot.
Frederic

For your information: this is the PHP code

 'info@maximgrimonprez.be', // Your Email Address
				'name' => 'Maxim Grimonprez' // Your Name
			);

// Form Processing Messages
$message_success = 'We hebben uw bericht **goed ontvangen**. We zullen zo spoedig mogelijk contact met u opnemen.';

// Add this only if you use reCaptcha with your Contact Forms
$recaptcha_secret = ''; // Your reCaptcha Secret

$mail = new PHPMailer();

// If you intend you use SMTP, add your SMTP Code after this Line

if( $_SERVER['REQUEST_METHOD'] == 'POST' ) {
	if( $_POST['template-contactform-email'] != '' ) {

		$name = isset( $_POST['template-contactform-name'] ) ? $_POST['template-contactform-name'] : '';
		$email = isset( $_POST['template-contactform-email'] ) ? $_POST['template-contactform-email'] : '';
		$phone = isset( $_POST['template-contactform-phone'] ) ? $_POST['template-contactform-phone'] : '';
		$subject = isset( $_POST['template-contactform-subject'] ) ? $_POST['template-contactform-subject'] : '';
		$message = isset( $_POST['template-contactform-message'] ) ? $_POST['template-contactform-message'] : '';

		$subject = isset($subject) ? $subject : 'Nieuw bericht via contactformulier www.maximgrimonprez.be';

		$botcheck = $_POST['template-contactform-botcheck'];

		if( $botcheck == '' ) {

			$mail->SetFrom( $email , $name );
			$mail->AddReplyTo( $email , $name );
			foreach( $toemails as $toemail ) {
				$mail->AddAddress( $toemail['email'] , $toemail['name'] );
			}
			$mail->Subject = $subject;

			$name = isset($name) ? "Naam: $name

" : '';
			$email = isset($email) ? "Email: $email

" : '';
			$phone = isset($phone) ? "GSM: $phone

" : '';
			$message = isset($message) ? "Bericht: $message

" : '';

			$referrer = $_SERVER['HTTP_REFERER'] ? '

Dit contactformulier is ingevuld via: ' . $_SERVER['HTTP_REFERER'] : '';

			$body = "$name $email $phone $message $referrer";

			// Runs only when reCaptcha is present in the Contact Form
			if( isset( $_POST['g-recaptcha-response'] ) ) {
				$recaptcha_response = $_POST['g-recaptcha-response'];
				$response = file_get_contents( "https://www.google.com/recaptcha/api/siteverify?secret=" . $recaptcha_secret . "&response=" . $recaptcha_response );

				$g_response = json_decode( $response );

				if ( $g_response->success !== true ) {
					echo '{ "alert": "error", "message": "Captcha not Validated! Please Try Again." }';
					die;
				}
			}

			// Uncomment the following Lines of Code if you want to Force reCaptcha Validation

			// if( !isset( $_POST['g-recaptcha-response'] ) ) {
			// 	echo '{ "alert": "error", "message": "Captcha not Submitted! Please Try Again." }';
			// 	die;
			// }

			$mail->MsgHTML( $body );
			$sendEmail = $mail->Send();

			if( $sendEmail == true ):
				echo '{ "alert": "success", "message": "' . $message_success . '" }';
			else:
				echo '{ "alert": "error", "message": "Uw bericht kon **niet** verzonden worden door een onverwacht probleem. Probeer later opnieuw.

**Reden:**
' . $mail->ErrorInfo . '" }';
			endif;
		} else {
			echo '{ "alert": "error", "message": "Bot **Detected**.! Clean yourself Botster.!" }';
		}
	} else {
		echo '{ "alert": "error", "message": "Gelieve **alle velden** in te vullen en probeer opnieuw." }';
	}
} else {
	echo '{ "alert": "error", "message": "Een **onverwacht probleem** deed zich voor. Probeer later opnieuw." }';
}

?>