I cannot find the house number of a house I am looking for, what can I do?
Kurviger is based on OpenStreetMap (OSM), see here for more details on OSM. Every house number has to be tagged by hand before it can be found correctly by a search request.
If you are keen to support the community, you could start tagging house numbers to help thousands of people. For more details on house numbers, have a look at the OSM wiki.