Note that if you are based outside Germany and you want to start a "Mahnverfahren" then you'll need to start it at the district court of Berlin-Wedding
Only do this yourself if you speak and read German well enough to handle the correspondence yourself. Otherwise you really need a German lawyer to act for you.
It is sometimes possible to agree payment of lawyer's fees according to the value in dispute instead of being billed for time spent. This can keep costs down.
https://www.mahngerichte.de/mahngerichte/wedding/
not at any other municipality's court.
Only do this yourself if you speak and read German well enough to handle the correspondence yourself. Otherwise you really need a German lawyer to act for you.
It is sometimes possible to agree payment of lawyer's fees according to the value in dispute instead of being billed for time spent. This can keep costs down.