All you need is a datatype for the Form Questions and a datatype for the Form Answers…
I’d also have an Option Set for Question Type
Then, your Users can create new Form Questions (with fields for the various possible input types - such as text, number, image, date, yes/no etc.), and a field to denote that Type of question, relating to the Option Set.
You can create forms to complete on your pages using Repeating Groups to show the Form Questions, with input elements set to show conditionally based on the Question Type (i.e. text input, date pickers, image uploaders, etc.).
Then, your Users can create responses to the various Questions, by creating new Form Answer entries, each relating to a specific Form Question.