I´m using contact form 7 on my webiste to get customers to order
products from my wordpress site.
But I want to let the user (customers) to add their own form feilds if they want to add other products then listed in the form.
Is that possible?
Fields in the CF7 creator are inserted as a kind of shortcode/internal format, and after that it passes a parser that changes them into valid HTML form elements. What you can do, is to use DOM (Document Object Model) to create a new element - but then, you should definitely pay attention to your PHP code afterwards.