Hi and welcome.
I do wish people would read the FAQ on updating the BIOS before just jumping in and trying it. No offence just an observation.
What you have done is brick your motherboard by corrupting the BIOS. Normally this would mean a dead board and garbage. However luckilly for you Gigabyte puts a Backup BIOS chip on the board and so we can hopefully get that to flash the Main BIOS chip and return your motherboard to working condition.
Before we go any further let me just give you some advice. If you want to update your BIOS don't use the
@BIOS program as it runs on top of the OS. Use the dedicated update tool
QFlash. It is much safer (as you have discovered).
The next bit of information can be tricky to get to work so you will just need to keep trying until you are successful.
You can kick in the backup BIOS by shutting down the PSU from the wall, then hold down your case power button in and then turn on the power supply button, a few seconds later the board will start, shut off the power supply then. Then you can turn on the power supply again and power up the board normally and DualBIOS will kick in.
Good luck.