If your friend has an address in Hamburg to ship to, I would recommend magierspiele.de. Reliable and they are located outskirts to Hamburg.
Actually they moved further to the north, a good two hour car drive away at least. So it is not as easy reachable anymore.
and about atlantis. unfortunately their website doesn't have any catalog of their games.
what sort of games do they usually have?
They have quite a big collection. Can't recall but they have more or less the standard stuff, Magic, a lot of board games etc..
and which store is usually sells at lower price? magierspiele or Atlantis?
Magierspiele for sure, but they are a online retailer with any service basically.