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.
Once your Goldfish have spawned, learn how to successfully raise your fry. The eggs should be kept at a temperature of between 70-75oF (21-24oC). At this temperature the eggs will hatch in 4 days. If the eggs are in water hotter or colder than this, the health and quality of the fry will be adversely affected.