Harry Potter & Wizarding Oblige

What would you do if GOD Sama asked you to prevent A Certain Wizarding World from impending doom? A SELF INSERT WF tale featuring MC as Cedric Diggory's younger brother.
First few years in known JKR HP verse but will later create my own for story building.
Persona, there will be no harem. In time, it will become slightly OP. This is my first time writing a narrative, and English is not my first language, so please help me if any changes are needed.