The number of Bitrix24 administrators depends on your plan. Therefore, changing a plan may require adjusting their number in your account.
Bitrix24 pricing page
Go to Company and open the Employees tab. Access the list of account administrators using the filter. If there is no Administrator field in the filter, add it manually using the Add Field section.
The list of active administrators will appear. Click on the name and go to the user's profile.
Select Revoke admin permissions in the Administrator menu.
Done! Now, that is a regular user without extended administrative rights.