I think there is only a slight difference. "Bu restoranda servis çok kötü." = "The service is very bad in this restaurant."
Using "ki" makes an adjective of restaurant. "Restorandaki servis çok kötü." = The restaurant's service is very bad."
Could EhabMohey92 please explain how 'restorandaki servis cok kotudu' means 'Service at this restaurant is very bad' and how 'Bu restoranda servis çok kötü' means 'The service at this restaurant is very bad'.
I disagree with EhabMohey92 that "The service" is more clear than just "Service" I am disappointed that no one else has commented on this. If no one does, then surely the programme should be corrected.