Ha, you are fast to find the seedy spots
Dunno about the current state but usually in that park you have a lot of competition, so it should be ok. People may be taking advantage of you obv not being local and not knowing the lay of the land though.
As for the pokers, welcome to our world. It's tough to find decent games with decent rake anywhere outside America, in Germany you often have neither. It's also tough to find a lot of non-weekend/holiday action anywhere in central Europe. But weekends should be better.
Cant meet up as I am in East Asia now but have fun in Berlin and explore the town at least a little. Berlin is great for many things, but the casino is probably not one of them.