How can I redirect respondents to another webpage after submitting the google form?

Google Forms does not have the option to redirect users to another webpage after submission. You can either customize the confirmation message to include a link so that this link is shown after submission, or use the Formfacade add-on to redirect users automatically to another webpage after submission.

How to redirect to a custom url after submission?

Pre-requisite: You must have installed the Formfacade add-on for Google Forms. If you haven't installed the add-on yet, you can install it from G Suite marketplace using this link.