I would like to suggest something for the original poster to check out; it might not work, but inquiries won't hurt!
The Estrel is a popular "Destination Hotel"; and apparently they have separate room blocks for use by airlines and travel/tour services. When we think of airlines and hotels, we first tend to think of them as transient air crew lodging, between flights. But such hotels are usually very near the airports served by the airlines, to minimise shuttle costs and lost rest time between flights. I don't know if this apllies to the Estrel, but I don't think that is is likely that the airline room blocks are for transient crews.
Well then - what else might an airline reserve a room (or block of rooms) for? To sell to tourists! Many airlines offer not just to fly you to a foreign destination, but to book your room for you too, as part of a package deal - especially if that room can be associated with something like a show, or convention, or other popular event! IF you currently have a reservation to fly into Berlin for EF, go to the webpage for your airline of choice and see if they can arrange to add lodging as part of the travel plan, and if the Estrel is one of their listed choice hotels.
Again - this may not work, but it is worth the effort of checking it out.
