Hi Manuel,
The issue here is that you're using German names for your countries, which aren't immediately recognized by the GeoChart, so it falls back to geocoding each name via Google Maps. This can get very slow, since the geocoder starts throttling you after 10 requests.
In order to speed it up, you could use the
ISO 3166-1 country codes, which the GeoChart knows about inherently, along with a second string column for "nice names". Alternatively, you could use english names for the countries, which the GeoChart also knows about.