Improvements on the site on Bitrix

We are looking for a developer to cooperate on a piece-by-piece basis on the development of the online store.

First of all, you need to eliminate the signature of the developer in the futer, as well as disable all access of third-party users.
There is a script that does not allow you to remove the user and returns the signature to the futer after deleting.

The developers company behaves inadequately, so we want to stop their access to the site. For the basic items that were part of the cost of developing the site now require a separate fee.