why the ventilator is making noise?

unet85 wrote:

why the ventilator of my MacBook Pro is making a fussy noise?

Keep your Mac notebook within acceptable operating temperatures

https://support.apple.com/en-us/HT201640

The fans are triggered for heat, whether ambient or that produced by computing activities or both.

CPU and GPU usage produces heat, and everything drawing power produces heat, too.

Fans can also have to work harder when the fans and cooling system are plugged with dust, too.

If your fan is making a noise such as a metallic grinding or failing-bearing noise, the fan might failing.

Have backups of your data; current and complete. These backups are your data-recovery path.