Helle Evryone , I juste wante to modifiy my file no-ota to file ota, i following the video in youtube https://www.youtube.com/watch?v=mRzZOa3jmuM but the problem whene I want to change start adress my application don't work

hello I want to update any firmware with app ST BLHello evryone, I want to create my own application BLE and update firmware via OTA, without using BLE examples existing like heartrate, and p2pserver.