Form resend datas after refresh on Symfony 6

Im beginner in Symfony :)

Ive created a website with Symfony 6.And i have a contact form page. This form work great but, after submit, if i reload the page, this form submit again.

Here, the ContactController

#[Route('/contact', name: 'contact')]
public function contact(ManagerRegistry $doctrine, Request $request, MailerInterface $mailer): Response
{

    $form = $this->createForm(ContactType::class);
    $form->handleRequest($request);
    if ($form->isSubmitted() && $form->isValid()) {
        $email = (new Email())
            ->to("contact@test-test.com")
            ->from($form->get("email")->getData())
            ->subject($form->get("title")->getData())
            ->text('Sending emails is fun again!')
            ->html('<p>See Twig integration for better HTML integration!</p>');

        try {
            $mailer->send($email);
            $resultMail = "Le mail est envoyé ! Pensez à consulter vos spams.";
            $this->addFlash(
                "success",
                "Votre message est bien envoyé."
            );
        } catch (TransportExceptionInterface $e) {
            // some error prevented the email sending; display an
            // error message or try to resend the message
            $resultMail = "Il y a eu une erreur lors de l'envoi de l'email.";
            $error = new Contact;
            $error->setEmail($form->get("email")->getData());
            $error->setTitle($form->get("title")->getData());
            $error->setMessage($form->get("message")->getData());
            $error->setDate(new DateTime());
            $error->setError($e);

            $em = $doctrine->getManager();
            $em->persist($error);
            $em->flush();
            $this->addFlash(
                "error",
                "Une erreur s'est produite lors de l'envoi de votre message."
            );
        }
    }

    return $this->render('contact/contact.html.twig', [
        "pageTitle" => "Contact",
        "ssTitle" => "Vous avez besoin de mes services ?",
        "contact_form" => $form->createView()
    ]);
}

How to fix it? And This is possible to redirect to contact anchor after submit ? (/contact#form) ?

Regards

After this snippet of code

$mailer->send($email);
$resultMail = "Le mail est envoyé ! Pensez à consulter vos spams.";
$this->addFlash(
  "success",
  "Votre message est bien envoyé."
);

you can place something like

return $this->redirectToRoute($routeName);

where $routeName is the name of the route (not the URL) where you want the user to be redirected if form contains valid data and mail is sent