chew your food well before swallowing it; don't eat too fast

life isn't beer and skittles, life's a bitch

Good deeds for the sake of others are unlikely to be met with gratitude, but are nevertheless honorable (and might be rewarded in the afterlife).

a sorrow shared is a sorrow halved

(childish) if you read this you're stupid (customary scribbling on school desks etc.)

Ellipsis of ist der Ruf erst ruiniert, lebt es sich ganz ungeniert.

something is rotten in the state of Denmark

a person’s silence can be very telling; usually in the sense that it can be understood as a negative or declining answer

(humorous) Said as a reply to a statement that is out of context, incomprehensible, unnecessarily complicated or detailed, etc.

all that glitters is not gold