If you wish to make the data files inaccessible to your restricted user, this can be done using file permissions but it will take some work.
what you need to do is remove
all their rights from the files / folders concerned, this is complicated due to the inherited rights that are in place
go to the root folder of the data you wish to hide, in the advanced security tab make sure that the "apply to subfolders ... " option is checked, but the "Inherit from parent... "option is not checked, this may generate a warning which should be accepted.
remove the entries
completely for all users or groups that you want to not allow access. This should include the everyone group plus any other general group for users, retain the rights for the administrator group, system, and any other user that needs access (including yourself)
when this is applied it will cascade down the folder tree. It works by denying the basic rights to view and navigate folders
Warning
removing the access for the everyone group without giving explicit permissions to at least one user can lock you out of these files completely. if this happens the hidden administrator account can be used to assign rights