Try
https://www.gutefrage.net/
Click on the little man in the top right to register .
Click on the hamburger sign and go to Alle Themen and it gives you a comprehensive menu.Loads of categories.
Within the last day or two I was looking through an AB member's old posts (I can't remember whose) and I spotted one where they were asking for a German version of AB. However, because it was posted ages (probably years) ago, I saw no point in replying. Then this post appears!
Shaney has beaten me to the first site that I would have suggested but there's also 'Who Knows What?'
http://www.wer-weiss-was.de/