You should always talk to your pediatrician first to determine the problem. If you have taken the recommended check-ups for the child, the pediatrician may already have recognized your child's problems. He can give you hints for specialists, e.g. Psychologists, psychotherapists who can help your child.
If you are concerned about your child's behavior or have significant difficulties with your child's daily interactions, a family or parenting advice center is the right person to contact. These can usually be found via the youth welfare office of your place of residence.
The health authorities in your city or region also provide advice and support. Health authorities of the federal state in which you live can be found on the website http://www.gesundheitsaemter-deutschland.de/gawebde.htm
Child and youth service in the health department Bremen
A list of the district teams in Bremen with contact persons you find here: www.gesundheitsamt.bremen.de/liste_der_stadtteilteams-2226
Health Department Bremerhaven: https://www.bremerhaven.de/de/verwaltung-politik/buergerservice/adressen-oeffnungszeiten/gesundheitsamt.22520.html
Child and Adolescent Psychiatry Counselling Centre and Outpatient Clinic (KIPSY)
Gesundheitsamt
Horner Straße 60-70
Eingang 6 (Klingel ist dort vorhanden)
28203 Bremen
+49 421 361 62 92
https://www.gesundheitsamt.bremen.de/detail.php?gsid=bremen125.c.1641.de
Family and Education Counseling Center Bremen: https://www.amtfuersozialedienste.bremen.de/kinder_jugendliche/erziehungsberatung_in_bremen___nach_stadtteilen__-4158
Parents phone http://www.elterntelefon.de/