OSM Germany is absolutely detailed. Honestly, german contributors could spare some time mapping in other countries.
OpenStreetMap community
Everything #OpenStreetMap related is welcome: software releases, showing of your work, questions about how to tag something, as long as it has to do with OpenStreetMap or OpenStreetMap-related software.
OpenStreetMap is a map of the world, created by people like you and free to use under an open license.
Join OpenStreetMap and start mapping: https://www.openstreetmap.org/.
There are many communication channels about OSM, many organized around a certain country or region. Discover them on https://openstreetmap.community/
https://mapcomplete.org/ is an easy-to-use website to view, edit and add points (such as shops, restaurants and others)
https://learnosm.org/en/ has a lot of information for beginners too.
And they contribute back to the project, right? Right?
Just switching by itself is a huge contribution.
And I also think they pay to use it, since commercial usage is not free.
since commercial usage is not free
Commercial usage oft the osm data is free, see the OSM license. The article even speculates that they switched from Google maps due to licenses costs.
Of course this doesn't apply to commercial services that provide e.g. map tiles.