[bierjunge]

Disclaimer: IANAL

In German law you don't have to assist law enforcement in building a case against you, so you don't need to provide passwords or say anything. But you can be forced to unlock your device via biometrics (fingerprint, faceID, etc.).

I'm not sure how it works, when law enforcement calls you as witness. The law changed a few years back, so you are required to assist them, but I'm not sure to which extent.