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.
yeah i am happy with 5-6 inches as long as the fish isn't thin and looks like it needs to grow a lot wider, as long as it has good body proportion to size im fine with that, but im happy to say that my goldfish who have shown no growth for the last 6 months have grown about half an inch longer in the last 2 weeks since i started feeding 4 times a day and also they have gone from being about half an inch wide to being an inch wide...but i think it could even be because they are females ...