Well, because I have succesfully logged using LDAP Path, I rewrited the problem:
The problem is, that when I use DirectorySearcher.FindAll() the individual DirectoryEntry.Guid (or .NativeGuid) does not match the DirectoryEntry.Guid (or .NativeGuid) returned when succesfully I log in.
(?) How to enumerate Guids of all users, which will be the same as the logged one?
or,
(?) How to access "not logged" user entry Guid if I am logged?
