Der Besserwisser — the better-knower. Someone who always knows better, and the word is a complaint.
Der Klugscheißer — the clever-shitter, cruder and more common.
Der Oberlehrer — the head teacher, applied to anyone lecturing an adult as though in a classroom.
Belehren — to instruct or lecture at someone, and sich belehren lassen, to allow oneself to be instructed, which is what you are asked to do gracefully.
Four German words for the person who gives advice nobody asked for. A culture does not develop that much vocabulary for a behaviour it rarely encounters.