@webdev Thanks for your help.
After many tests, headaches, and reaching out to them (support couldn’t handle technical questions), I decided to drop out of ConvertKit.
I found out that they have a very good affiliate program, and therefore all the posts and advertising favors them but they don’t live up to the expectation.
I’m going to go with Autopilot which is an amazing tool. No form needs to be hooked up, just by adding a JS code snippet on the header (Custom Code), Autopilot detects every form on the site and gathers the data you need 
Also, Autopilot is 100% GDPR compliant, providing even a GDPR contract to sign.