This linguistic confusion is why Americans call the Pennsylvania Dutch Dutch even though they're Germans. To review: this country is the Netherlands, its people are Dutch, they speak Dutch. There is no country called Holland, but there are provinces of North and South Holland.
In clean, uncrowded conditions in tanks or ponds, goldfish grow fast. They can grow to a few inches (1 to 4 inches) within the first year. It really depends on their genetics and living situation. It may take a year or two before they change color from brown to gold or whatever color their parents were.
1 Sadly, many goldfish never live long enough to even grow the 8 inches, 10 inches, or even 20 inches long their body was destined to be.  Water changes can be very stressful in a small goldfish tank. Goldfish prefer water that maintains a constant temperature. A small aquarium just canât hold enough water mass.