I need help really bad pls.. Its about directx?

ok so here's my story one day my older brother just updated my directx to 11. now all my games stopped working and he said he wont help me because if he breaks something my parents will blame him. So i looked online for like 5 hours everyday and i still dnt know how to change it back to 9.0c. or just degrade it or something. i just dnt want it directx 11. so i heard that if u erase your direct x file on regedit on run everything would go back to normal wrong. i tried it deleted my directx file and nothing happened so theres my story. i dont how to make the file reappear i i dont know how to do everything so anyone pls help me with my directx 11 to directx 9.0c mission. PLSSSS!!! Thank you