How to Collect Response Data from an Embedded Survey on my Web App?

Just a newbie programming student here tasked with creating an app that gives access to a survey that sends its data to Google BigQuery. Currently, I just have the survey embedded on my web app via an iframe. I'm not sure if this is the practice but regardless which APIs would I have to use and how to use it in order to collect the single response's data? I would imagine I would have to pass in some parameter into the embedded survey url or edit the javascript in the survey to include a function that sends data back with offLoad()?