Better with "Make a change" only ? no more create a new data?

Hello everyone !

I am building a new app and i was wondering why we use so many times “Create a new data”, instead of “modify a data”, especially with forms

For example, i have an app that the user should fill in more than 50 inputs. I have parsed it in two pages : one to create the form / fill in the form and one to modify the information of the form.

Tomorrow, if i want to add new inputs or if i want to modify the design, i have to modify my two pages (create and modify) => double work . I was wondering, why in many tutorials, they do not advise to create only one page “modify” ? => when the user click on “fill in the form”, it creates a new row in the database (but without information), then the user go the the page “modify” and can “fill in” blank item and save it

Could someone help me to understand ?

Thank you : )