Hi Samed,
The way I see this, the QR-code basically is just a visual representation of a code that refers to your form. So, when the user fills out the form and saves this, you can generate a random code (maybe a GUID) and store this in the record that holds the form data. Then you generate a QR-code from this code and show that on the screen. Then when the use scans the code, you query the correct record that has that code and fill the form with that data, so the user can edit it.
Goodluck!
Lennart