Rzucać grochem o ścianę

Literally: To throw peas at the wall

Example: “Tłumaczyć mu zasady to jak rzucać grochem o ścianę.” — Explaining the rules to him is like talking to a brick wall.

English equivalent: Like talking to a brick wall

Origin: Dried peas thrown at a wall bounce off and leave no mark, which is how Polish Wiktionary explains the phrase: "from observation." Throwing peas at a wall is trying to persuade, teach or warn someone with no effect at all. Russian has the same image, как об стенку горох (like peas against a wall).