How can I know who answer my survey ?

When I send out a survey the answers come back to me but not who answered them.

Without my customers having to write their name or email at the end of the survey.

Hi,

If they don't fill in their name and email, I don't think you will find out who did the survey. 

Since your name and email field are not required fields, it is possible for them to skip these fields. I would suggest to make it required so they can't submit the form until they provide their name and email.

To those who submitted the form without their name and email, you can somehow get their location and IP address by going to form analytics page.

Example: