My English is like that too. On the internet, in books, movies, tv shows, radio, music... it's all different kinds of English I listen to and read. If I lived in an English speaking community that wouldn't matter, but the people I speak English with day to day also have all different Englishes.

I could read a lot, sure. I do think I ought to read more books, because I've gotten out of the habit. But written English is not like spoken English. It might be all right for narration, but it's wrong for dialog.

I do actually like to challenge myself exactly like that :-)

Perhaps trying to write the Danish you use when the audience doesn't know English?

I don't understand what you mean. For improving my Danish?