If you actually want to dress up as a character from “Money Heist”, “Squid Game” or in general with a mask, you should also observe the ban on disguise.
It is fundamentally forbidden in Germany to cover your face on the way to and at public meetings or other public events that take place outdoors, as well as in traffic, so that everyone can be identified.
Although events such as Halloween and Mardi Gras are traditional festivals and can therefore be exempted from the former bans according to the legislature, face coverings are still prohibited in road traffic and can be punished with a fine of 60 euros.
So you should definitely take off your head and face costumes on the way to the Halloween party.