Make a safety landing at BER - no traffic there ;-).
EDAZ would be natural choice for Berlin, you could either rent a car, or take the EDAZ-shuttle to the train station (25 min ride to Berlin). This is probably the best GA field in Germany.
EDOI would be another famous choice. Shuttle to the train station available (35 min ride to Berlin center).
EDAY also offers shuttle to train station (3 min drive and 45 min train to Berlin) and has a very nice service culture.
There are a couple of more small fields around EDDB, but most of them are in infrastructure desert areas. Many time somebody will take you to somewhere, but I would choose one of the three above, if EDDB is unwanted (it is not a bad airport for GA though, only transport from GAT a bit tricky).