(idiomatic) I know (of) nothing; I am not involved

there's no smoke without fire

the coast is clear

the penny drops

I don't care

(informal, humorous, slightly dated) Used when granting entry to someone who knocks at the door.

Alternative form of dieser Zug ist abgefahren

that ship has sailed

third-person singular present of auf dem Holzweg sein

how did it go?