Hi there,

If you're editing as part of an organisation, you'll need to be aware of the Organised Editing Guidelines [1].

With the edits themselves, I'd start by making sure you've pulled down what already exists in OSM, edit those, and then upload it. If you just add data to a blank JOSM workspace and upload it, it will only ever add new data, not replace any existing data.

[1] https://wiki.openstreetmap.org/wiki/Organised_Editing/Guidelines