I recall that this hotline basically just calls your local authorities and prevents you from being a danger to yourself by having you committed to a mental health facility. Sub-optimal.
The easiest way to access a therapist is to ask your general practitioner (Hausarzt or Allgemeinmediziner) for a referral. You'll still have to find one yourself but they can direct you towards a list. The wait times can be very long but the sessions (and meds if any) are covered by public health insurance.
First they will talk you down if there is imminent danger. There are some real skilled people that are good at de-escalation. They might try to get you in touch with any fiends or relatives you may trust, and even conference them into the call with your permission. (I was called by them.)
They can also dispatch a team to help calm down any acute episode of severe depression / suicide ideation.
They can recommends a voluntary committment to a mental health facility. Involontary committment has certain criteria regarding safety and imminent danger, at which point it would involve the police and they would be the ones making that call.
If not a mental health facility, they do recommend getting a psychiatrist ASAP and provide referrals. And they call back a few days to check on the caller, to ensure they followed through and are seeking help.
Source: A close relative experienced this first hand.
Its a rare thing and highlighting it as the default scenario is spreading FUD and possibly keeping people from getting the help they need. It is true though that if you call and describe an immediate plan to kill yourself there is some legal, ethical, and liability requirements that mean they will call authorities. Exact same thing if you tell your doctor or therapist.