Strategy to find out about user goals after the product is made

I'm a coder, I made a product long back and I just read my first UX book. I learned about 'user goals'.

I do not assume anymore that my product solves them.

  1. I am unable to make a strategy for going ahead and fixing the entire website so it actually helps its visitors.
  2. How can I setup a survey to honestly learn about user goals/expectations?

The product is non-profit/activism.