The deactivation / activation is done via the account holder himself or a user with administrator rights. You can not deactivate your own user.
To enable / disable the employees you can retire to your company profile .
Now call the tab page "staff" (1) and then click on the "All Listings" (2).
A list of all employees (including the disabled user) appears.
Here you can now select the desired employee.
Depending on the current employee status (whether disabled or not) appears in the title element "permissions" the / button option "Disable User" or "Activate User" (see below).
Here you can now activate or deactivate the user via the corresponding button.