Wait until the employer has signalled interest or made an offer. Leading with hour limits in the first screening call can close doors before your skills are visible.
Prepare a concrete proposal: preferred days, core hours you can cover, and how handovers would work. German employers respond better to a schedule sketch than to open-ended flexibility requests.
Name the care reason briefly if asked. You do not owe a full family history. 'I have school-age childcare on Mondays and Wednesdays until 14:00' is clearer than 'I need work-life balance.'
Know the legal backdrop without quoting statutes in the meeting. Teilzeitansprüche exist in many cases, but a collaborative tone usually works faster than a rights lecture at the offer stage.
If the employer refuses, ask what pattern they could accept. Sometimes a 30-hour week with one remote day is available when a classic 50% split is not.