Ola. You mean Berlin, the capital of Germany (DE)??

It is not clear as you state to see a lot and ask about nighttrains=not see much, you sleep and its dark.

BUT you MAY be able to use overnight train from Hendaya (go ther by Eskotren from Donostia=pay ticket) OR from Cerbere =border ES-FR along mediterranee, rodalies tren from Barca, to Paris (in fact these portions of train are joined in Toulouse).

Also there are-not daily- Overnight trains from Paris to Austria (Nightjet, book via oebb.at) get off as some point before and make a nice trip to Berlin , even can go via Praha, golden city.

OR there is-not daily- a seats only kind of train running in the night In DE from Köln to Berlin, and many more, ev, hour in the day