“Was Hänschen nicht lernt, lernt Hans nimmer mehr.”
A famous German proverb that basically says what people don’t learn as kids, they won’t learn as adults and it’s basically about manners and good conduct.
The literal translation is roughly:
“What small Hans doesn’t learn, Hans won’t ever learn.”
-chen is a super common ending to make someone or something small and cute. And they’re always “das”.
“nimmer mehr” is outdated and only used in books and old sayings.