Coins in Berlin

So, I'm going to visit Berlin for one week. Can you suggest any places or markets where I can buy some good coins for reasonable price?

I dont know about the prices but this shop was referred to on the Numista list.
https://en.numista.com/outings/munzen-am-zoo-berlin-565.html

In the area of Bernauerstraße on Sundays there are markets with quite a few dealers in all kinds of new and old things, including coins. Last year I got a few GDR coins as well as a Nazi 5 Marks. Some will ask for too high prices, so you have to make an offer.

You can combine that with a visit of the remains of the Wall along Bernauerstraße. This is one of the main areas to learn about the Wall.

Nothing to buy but to watch: You should definitely visit the coin collection of the Bode-Museum on the Museums-Insel.

https://www.smb.museum/en/museums-institutions/muenzkabinett/home.html
https://en.wikipedia.org/wiki/Museum_Island