[SOLVED] Why this happens??

Solution
Does look like artifacting. Is it possible to RMA your card still? If not, would you be able to test the GPU in another system? If the behavior persists, you'll need a new card sooner or later. Meanwhile, at least you can play what works. If you can't, you could try software troubleshooting, but it appears hardware related, and it isn't from overheating.
Does look like artifacting. Is it possible to RMA your card still? If not, would you be able to test the GPU in another system? If the behavior persists, you'll need a new card sooner or later. Meanwhile, at least you can play what works. If you can't, you could try software troubleshooting, but it appears hardware related, and it isn't from overheating.
 
Solution
Certain those little specs aren't part of the game? Maybe needs to look like snow.

Which version of the motherboard do you have? Need to know before updating bios. With Gigabyte there is probably a marking on the left lower corner of the motherboard or check the box it came in.