Make backend-level edits for bitrix site

There is a website on Bitrix. It has a lot of small edits that need to be made when working at the code level with the control system itself: somewhere change the text, somewhere the logic of displaying the title, somewhere speeding up the logic of the callback.

You need a strong knowledge of Bitrix itself, so in the response please indicate your experience of working with this control system. Better with specific links.