In all cases you will receive advice and help from the responsible youth welfare office and the addiction counseling centers.
Youth welfare offices in Sachsen: https://www.sms.sachsen.de/11324.html
Important information can be found here: https://www.suchtfragen.de/ and https://www.hls-online.org/
Addiction counseling centers in Sachsen can be found on the website of the state office against addictions in Sachsen: http://www.slsev.de/suchthilfe/elternkreise/