Hi Christina,
you can find more information on the issue in the OSM-wiki in this article:
https://wiki.openstreetmap.org/wiki/Changeset#Geographical_size_of_changesets

But don't worry too much. Keep working, especially the "white spots" of the map.

Here are some more links that can help
https://wiki.openstreetmap.org/wiki/Good_practice
https://wiki.openstreetmap.org/wiki/DE:How_to_map_a
https://wiki.openstreetmap.org/wiki/DE:Beginners%27_guide
https://wiki.openstreetmap.org/wiki/Contact_channels#Chats.2Fmessengers

happy mapping
silversurfer83
