Where is the admin controller stored in Bitrix?

Question

1C-Bitrix

They gave me a project on Bitrix, but I have only one question, I can’t determine where in Bitrix for the page localhost/bitrix/admin/user_edit.php?lang=ru&ID=1108858
But I don’t understand how to make a rule when saving and therefore I need a controller, but I don't know where it is

Answer 1

It is better not to touch the standard pages, because. The update will overwrite everything.
It's better to create a separate page or use events