Please do not send any documents (company invitations, hotel bookings, etc.) separately to the Embassy unless you have been requested to do so by the German Embassy. All required documents have to be handed in together with the visa application. Information for German hosts about a cost guarantee according to §§ 66-68 AufenthG (as signed company letter or official obligation form from “Ausländeramt”) can be found here
The German Embassy Kuwait reserves the right to ask for additional documents and /or call applicant for an interview at any time.