The number of Bitrix24 administrators depends on your plan. Therefore, changing a plan may require adjusting their number in your account.
Go to Company > Employees section, and search for administrators in 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 employee's profile.
Select Revoke admin permissions in the Administrator menu.
Done! Now, that is a regular user without extended administrative rights.