Google claims they allow (for the free plan) 15,000 requests/month and I was usually able to use the node within these dimensions, but probably they introduced some more restrictive rate limiting recently (afair there was a similar post recently). You might want to try running this in chunks and introduce a Wait in between or give the other Geocoder node a try:
For your data, also the Palladian Location Extractor might be well suited, as you’re obviously only interested in City-level accuracy (and not full street address geocoding):
If you want to give this a try, I would simply concatenate all place names per row into one line, such as ort landkreis bundesland and the extractor should be able to disambiguate to the appropriate location automatically. It uses the Geonames API and provides an optional integration with locally running Gazetteers for higher request volumes and/or privacy.
Execute failed: No LocationSources are enabled, thus no locations can be extracted. Please check the settings and activate at least one LocationSource.
Settings of KNIME / Palladin or Setting of mapquest.com ?