[otrs] newcomer questions

Hello Finally I found the time to install otrs on my system. I had a look into it quite a time ago and was fascinated, but now it's even better. Anyway, during the installation some questions came up: - can I setup queues, which are invisible to customers (queues for internal use only) - How can I delete existing queues (is it ok, to just delete them from the database?) - Is there a way to disable new account per default if the customer has registered through customer.pl. i.e. to let someone from internal review the application before it's usable? Thanks a lot in advance Andre