The first contact for safety issues is the police authority (call number 110). In case of a risk to the child's well-being through neglect or mistreatment the Youth Welfare Office (General Social Service) should be contacted.
Youth welfare offices in Baden-Württemberg: https://www.kinderinfo.de/jugendaemter/baden-wuerttemberg/
Child protection centres: http://www.kinderschutz-zentren.org/zentren-vor-ort
Emergency service for children and youngster https://www.service-bw.de/lebenslage/-/sbw/Beratung+und+Hilfe-5000072-lebenslage-0