Redirect user to previous page after registration

I'd like users registering on my website are redirected to the page where they clicked the "create account" button which is in a modal.

First, I tried to redirect to an absolute urlI tried

$form_state->setRedirect($myUrl);

I tried

$_REQUEST['destination'] = '<front>';

I tried this too :

$response = new \Drupal\Core\Routing\TrustedRedirectResponse('http://www.google.be');$form_state->setResponse($response);

I'm always redirected to /user/[uid]/edit