I looked up the Potsdam meeting you mentioned and there were literally members of CDU (Merkel's party) present as well. It's utterly laughable to try and use that to then exclusively castigate a different political party for having had some of its members present. By your illogic, we would be forced to infer that the CDU is also "extremist".
So far, I'm left feeling like AfD has indeed been misrepresented by the liberal western media. And, I say this as someone who certainly does not agree with some of their positions. For example, being "skeptical" about climate change in 2026 is sheer idiocy.
But what is very clear to me is that Germany has a democracy problem. The system as described has not been truly democratic. It instead sounds approximately 'left-leaning authoritarian', right down to your insinuation that a political party should have been banned for its speech.
In case anyone in Germany is interested in rediscovering democracy, please note that THIS is what it looks like: “I disapprove of what you say, but I will defend to the death your right to say it.”