Thank you Danhiel an RolandP!
So, if i understand the information on the website right: we go to an Office on the Day of arrival with our identity card, photo and address of the hotel. Then the Swiss Pass will be delivered by post and in the mean time we can get a temporary Swiss Pass that is valid from the day itself, and we can buy a GA Travel card for one month at that same moment?
That would be great if that works.