The Dutch rank #1 in the world in English-as-a-foreign-language proficiency, and they have been ranking #1 consistently every year for many years now, according to yearly reports by the Education First (EF) organization. (Wikipedia.)
I can attest that at least in the Randstad area, (where half the population of the country lives,) almost everyone speaks English, and many do so very fluently.
Nonetheless, there are certain mistakes that the Dutch are somewhat prone to make in English, mostly due to interference from peculiarities of the Dutch language. When this happens, it is called Dutchlish or Dunglish. The phenomenon is acknowledged by the Dutch, who have their own word for it: Steenkolenengels, which literally means coal-English.
Here is a long list of examples of Steenkolenengels that I have compiled over the course of several years of living in The Netherlands.
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