How can I make the survey save responses and come back to it?

If I understood you correctly, you want to allow your users to save form and continue later. If that is the case, you might consider using one of the following options:

1. How to Enable Auto fill feature - save form entries to continue later 

Auto fill method is based on browser local storage. It is saving the form data on users browser, so user can open the form later and he/she will see the past data. Note - user will need to use same computer and same browser to access data.

2. How to save form to continue later (Session method)

The Session method is saving the data on our servers. With this method you will need to use two forms, one for session generation and second as primary. Then users will be able to access their sessions from any locations.

Hope this will help. Let us know if you need further assistance.