What questions do I ask customers after they indicate interest from Facebook Ads?

I spent a year building a product with no customer feedback. I personally know three businesses who need this product. Now the product is almost done, and on the frontpage is a form that customers (usually small businesses) can fill to "Request more information".I started running facebook ads targeting small businesses, and I am getting "More Info" requests at a cost of about 30cents per info request. They provide their email and their phone number. I have about 10 such requests per day.I want to now talk to these users to understand what exactly they want, and possibly adapt the product. Is there a structured way to go about this? Is there any official "theory" about the best way to talk to users in an open ended manner to allow you discover how your product may not be right for them, but there is an adjacent product that could be build? see hubwealthy.com/wealthy