be banging, etc. your head against a brick wall

be banging (one's) head against a brick wall

To be attempting, continuously and fruitlessly, to accomplish some task or achieve some goal that is or seems ultimately hopeless. I feel like I've been banging my head against a brick wall trying to understand this math equation.
See also: bang, brick, head, wall
Farlex Dictionary of Idioms.

be banging, etc. your head against a brick ˈwall

(informal) try for a long time to achieve something, persuade somebody to do something, etc. without success: I realized they weren’t even listening to my protests. I was just banging my head against a brick wall.
See also: brick, head, wall
Farlex Partner Idioms Dictionary
See also:
  • be banging (one's) head against a brick wall
  • be banging your head against a brick wall
  • be hitting (one's) head against a (brick) wall
  • beat (one's) head against a stone wall
  • knock (one's) head against a (brick) wall
  • knock (one's) head against a/the wall
  • knock head against a brick wall
  • bang (one's) head against a brick wall
  • bang (one's) head against a wall
  • bang your head against a brick wall