Volume buttons nou working

Hi Shahid,

Assuming the physical button you press on is intact, the only other part that can go wrong is the switch that provides the electrical connection and the click action. On your phone all three side buttons, power and volume up/down, are built into one little flex cable that can be replaced. Sorry to say that we don't have a guide here on iFixit, but there's a Spanish site called Nadie Me Llama Gallina that has just what you need.

Manuales / Xiaomi Redmi 9 / Side pushbuttons

That should get you going; let us know if you need any advice along the way!