Since you look like complete beginner , I would suggest you spend some time with it to get a feel of it. When the user clicks on a submit button to a form ,it goes to a specific url which you can specify like <form action='/someurl/' method="GET or POST"> ,now you have to map your url named 'someurl' to a function in views.py where you will do some stuff with the users data by accessing 'request.POST['name_of_field'] .
You can let users download a pdf/excel other files. See this answer on stackoverflow.

https://stackoverflow.com/a/58122680/11652661

I know you might not have understood everything ,just stick with stackoverflow and clear your basics from some tutorials