The cards are backwards compatible, it will just run at pcie 2.0 which won't make a huge difference anyway.I would suggest updating your bios prior to installing the card though.
The board is PCI-E 2.0 and nothing won't change that. The bios update is meant for ensuring compatibility. As xmad said a 3.0 card will work fine in a 2.0 slot.
i download the bios from live update and i installed it with .exe ... is this right?...
It's maximum risk but as you already did it and it worked fine. The new .exe bios versions in fact can just be flashed with the method it comes with.
Unfortunately currently the only way is the .exe method.