Oliver gave you a great start and I won't be able to improve on it since I don't live near the Berlin area either. However, my experience with finding Festool dealers using the Festool.de site has been disappointing.
My favorite stocking Festool dealer in Mannheim closed several years ago. I was able to buy most of what I wanted from their stock, but some items, such as the VAC SYS1 and SYS2, had to be ordered. Even then, the wait was three or four days and I had my option of a store pick-up or having the item drop shipped to my house at no additional cost. I always chose the store pick-up because I liked the employees.
My new favorite stocking dealer is a bit closer, but has a small fraction of the inventory of the previous store. As with the first favorite, anything I want from the catalog, and not in stock, can be delivered in a few days. I bought a router from store stock, but the rest of the tools had to be ordered. While I also like the employees at the new store, the street access and availability of parking make it difficult to visit, so I now have everything drop shipped to my house and communicate with them via phone or email. It is still a brick and mortar business and preferable to me over a strictly online transaction.
As a point of reference, a quick search of the Festool dealers in Mannheim, from the Festool.de website, shows six stores within the immediate Mannheim area. I visited three of them, and only one had any Festool items in stock. Unfortunately, the Festool items were sandpaper because the primary focus of the businesses was paint and painting supplies.
I can appreciate the desire to visit a stocking distributor in person; however, if your stay in Berlin is limited, you might want to consider placing an order from an online vendor and have the shipment delivered to the hotel. I did this many years ago when I was visiting the States and wanted a Timex watch that was not available in Europe.