Christian-Red-Owl You can ask at Reisebank, they have branches at most central stations or at airports
Question is if that's less expensive than at Sparkasse. Hamburger Sparkasse (as the biggest in Germany) gave you 1.0640 USD per EUR today. Reisebank, according to their website at the moment has a rate of 1.07. Not much of a difference. Other retail banks might have better rates. I just checked Commerzbank at 1.0898.
Jul I would just withdraw at an ATM at the airport when you arrive.
Always check the rates, especially at ATMs inside Airports.
For instance, I recently saw 10%+ currency exchange margin offered through DCC (Dynamic Currency Conversion) for GBP after arriving in London - and you couldn't even continue with declining DCC for some reason (well, clearly we know the reason).
That said, I'd generally get cash in the destination country - unless in special circumstances: ATMs you can't or won't trust, entering the country through smaller points/ports of entry where there might not be an ATM, etc...
In this specific case, the U.S. is such a popular traveling destination and the USD so widely used even outside of the US ...there's a good chance some friends or colleagues still have a few Dollars left-over from their own travels and would be happy to exchange them with me at a fair (interbank) rate.