Hi Shirsendu_983,
I'm Rodrigo and I will help you.
Gigabyte motherboards have the Ultrafast boot, which boots very fast but doesn't let you access the BIOS setup.
To access the BIOS setup, open the Start Menu > Power > Hold Shift and click on Restart. This will force the system to boot on the recovery environment.
On the Recovery Environment > Go to Troubleshoot > Advanced Options > and select UEFI Firmware Settings > Restart.