Dianabol what is it?

I read that it is often used by bodybuilders to gain muscle mass and strength. They especially note that it starts to act quite quickly, which makes it popular for those who are in the mass gain phase. I want to know more about its effect, dosages and possible side effects. What are the pros and cons of this drug? And how to take it correctly to minimize health risks? I would be glad if someone shared their experience or gave advice on where to buy a quality product.