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 have natural life span of over 20~30 years, if your goal is only a few months, it's like getting a puppy and expect it to live a few months and you will be fine with that. No fish should be in a fishbowl. Those bowls aren't for fish keeping, it's nothing more than marketing. Fishbowls are in fact fish killers.