thank you so much for answering all our questions.
Since I have never worked with CodeIgniter its just a bit confusing to find things.
So one more question:
How can I deactivate reviews completly or which files do I have to modify to get rid of everything which has to do with reviews?
Getting rid of reviews will require changes to a lot of files since it is part of the core. However, i think the system should have an option to disable or enable reviews from the administrator panel, just like reservations. I will mark this thread and get back to you.