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.
Goldfish are very large compared to many tropical fish species. Most fancy goldfish varieties grow up to 6 or 7 inches long (15 or 18 centimeters), while common and comet goldfish can grow to a foot long (30 centimeters) and even more. Though there are exceptions, tropical fish tend to stay small.