English is the language of the Internet. If you are the monoglot citizen of a country like Denmark, you are—through no fault of your own—restricted to an audience the size of metropolitan San Francisco.
Even for the native speakers of a major European language such as German, English is the only available ticket to a global readership.
This is why virtually everybody nowadays blogs in English.
Writing in a foreign language, however, is not an easy skill to acquire. I am not suggesting that simply by reading this article, you will become a fluent writer. But I can show you how to get there—and point out some of the most dangerous traps along the way...