You can find a text list of all the files within /Test nach webDav and nested folders here: http://files.asys-it.de/Test%20nach%20webDav/?raw
To download /Test nach webDav and all nested folders with aria2c you can do this:
> curl http://files.asys-it.de/Test%20nach%20webDav/?aria2 | aria2c -c -i -