In February 2019, OpenAI published a blog entry on the GPT-2 laguage model that allows to create high-quality artificial texts in English language.
For German, a pre-trained model is made available by Zamia Brain. Although it is based on a much smaller text corpus, it can be used to create quite impressive artificial German texts.
A demo application is available at jupiter.fh-swf.de/fake_text.