Hi Gerd Wagner,
I have updated that section. You should be paying attention to the meta description, not the meta tags. Here’s the official Google word on it: https://support.google.com/webmasters/answer/79812?hl=en
I didn’t talk about structured data because I wanted to write an article that everyone could read, understand, and implement. There’s always technical details that can be done to further optimize content, but I wanted to write something accessible to everyone.