In all cases you will receive advice and help from the responsible youth welfare office and the addiction counseling centers.
Youth welfare offices in Rheinland-Pfalz: https://kita.rlp.de/fileadmin/kita/01_Themen/01_Wir_ueber_uns/Jugendaemter_rlp.pdf
Important information can be found here: https://www.suchtfragen.de/ and https://www.hls-online.org/
Addiction counseling centers in Rheinland-Pfalz can be found at: https://lsjv.rlp.de/fileadmin/lsjv/Dateien/Aufgaben/Kinder_Jugend_Familie/Adressen/Beratungsstellen_Sucht_RLP.pdf