You could start with this app: https://github.com/westnordost/StreetComplete https://github.com/westnordost/StreetComplete It's super easy and once you run ou

You could start with this app: https://github.com/westnordost/StreetComplete https://github.com/westnordost/StreetComplete It's super easy and once you run out of tasks, you can dig in deeper with this one https://wiki.openstreetmap.org/wiki/Vespucci https://wiki.openstreetmap.org/wiki/Vespucci or just through the browser. Germany is quite well documented.