Im not worrying if it works or not im just asking if it is any harmful or not and i just wander on how i can change the number of cores running
That's like asking if having 6 cylinders in your car is "harmful". If you have a 6 cylinder motor, having 6 cylinders is not harmful.
If you want to disable some of your computing power, you can do so in your BIOS. However, I would not recommend you do so until you understand what you are doing and why.
Making the wrong adjustments in your BIOS is something that can be harmful. It's like adjusting the A/F ratio or boost on a car. If you know what you are doing, you can make the car perform better. If you don't know what you are doing, you can "harm" your car.
Your CPU is supposed to run on six cores. I recommend leaving it alone.