In all cases you will receive advice and help from the responsible youth welfare office and the addiction counseling centers.
Youth welfare offices Nordrhein-Westfalen: https://www.kinderinfo.de/jugendaemter/nordrhein-westfalen/
Important information can be found here: https://www.suchtfragen.de/ and https://www.hls-online.org/
Addiction counseling centers in Nordrhein-Westfalen can be found at: http://www.landesstellesucht-nrw.de/suchthilfedatenbank.html
http://www.kmdd.de/adressen-und-links-zur-sucht--und-drogenberatung-deutschland.htm