We'll create fresh WordPress site with Simple Redirect – Contact Form 7 installed. You have 20 minutes to test the plugin after that site we'll be deleted.
Redirect settings for Contact Form 7, Redirect after mail sent or form submit, Add settings line in form “Additional Settings” tab,
on_mailsent_redirect_to: REDIRECT_URL
on_submit_redirect_to: REDIRECT_URL
Example:
on_mailsent_redirect_to: https://www.example.com/thank-you/
on_submit_redirect_to: https://www.example.com/step-2/