Flutter Gmax IPTV App Email Login Modification

I would like to modify the Flutter Gmax IPTV application (https://codecanyon.net/item/gmax-iptv-xtream-flutter-app-android-ios-macos-windows-/49524116) to replace the current authentication method with an email and password login. I will provide access to my XUI One panel for configuration. Please confirm your availability and your rate for this modification.