in my macbook sound automatically decrease after 2 second

Try and restart the mac to see if the issues persist

If they persist boot the mac in the safe mode to see if the issues persist. If they don’t persist in safe mode, they are most likely caused by an external piece of software

Start up your Mac with Apple silicon in safe mode

1. On your Mac, choose Apple menu  > Shut Down.
2. Wait for your Mac to shut down completely. A Mac is completely shut down when the screen is black and any lights (including in the Touch Bar) are off.
3. Press and hold the power button on your Mac until “Loading startup options” appears.
4. Select a volume.
5. Press and hold the Shift key, then click Continue in Safe Mode.
6. The computer restarts automatically. When the login window appears, you should see “Safe Boot” in the menu bar.