“The Science of Well-Being”
Coursera (English) ~ 19 hrs, 3/week

Wildly popular class at Yale on happiness, well-being and other elements of positive psychology - including exercises, daily habit-changing and integration into real life

“Young people and their mental health”
Class-Central/Future Learn (English/Dutch) ~5 hrs, 2/week

Similar class from University of Cambridge/Groningen but maybe addressing a bit younger audience than ours - might be helpful nonetheless

“Positive Psychiatry and Mental Health”
University of Sydney (English) ~ 21 hrs, 5/week

Mental Health First Aid Program

A course that improves the general knowledge about mental health and increases confidence in one's own helping skills and strengthens one's own mental health. The website is in German, but they offer this course in English, too.