creating interactive web forms on Mac

This has nothing to do with Apple's Pages word-processing application. Your ask is beyond the scope of the Apple Support Communities.

If you know nothing about HTML/CSS3/JavaScript/PHP or how to create a web page/web forms in a plain text editor, then you won't find this easy at all. You should find someone who does this for a living and seek their help, or be prepared for a lengthy uphill learning process. All you need to know can be found on the Internet with a search engine if you are willing to invest your time.