The inside-the-law approach that works to some limited extent is public community rejection. Things like large groups showing up and standing with their back to the Nazis.
The method that has historically stopped Nazis like this involves getting some level of police cooperation and beating them up
In Germany we (meaning other people, not me) usually organize counter-demonstrations.
Isn’t it very illegal to be one in Germany? Shouldn’t the police be arresting them?
There are certain symbols (like the Swastika) that are illegal, but just believing you are a superior race isn’t against the law.
We did that here. The media called us AntiFa and the cops tear gassed us and assaulted people with mobility aides. Then we started getting arrested and people who escaped were followed home by the Nazis. Knowing what happened I still would have gone, but I would have prepared better