Using external ID

The fastest and easiest way to create a map like you say is umap.openstreetmap.fr - just create a JSON file with the pharamacies, open it on umap, and you're done!

In order to import data into OpenStreetMap, you need to follow the import guidelines (https://wiki.openstreetmap.org/wiki/Import). Please pause any activities adding data to OSM until you have read and understood these guidelines.

Among other things, we need to establish:

1. Are the sources that you want to use cleared from a copyright point of view? You say that you have "a few sources" and it is unclear what the license is on those; just because someone in the government has given you a few lists doesn't necessarily mean anything.

2. What is the data quality like? Do you have the local knowledge (or additional sources) to verify the data? More often than not, such data sets have had their lat/lon created by throwing an address into a geocoder which can lead to copyright issues (see 1) but also to locations that are hundreds of metres away from the correct spot (occasionally even in a different city).

3. What exactly is your procedure to "synchronize" with what is already in OSM?

Using an "umap" for your project is quick way of getting something done that you can show to the government; we can then take the necessary time to vet the dataset for import in OpenStreetMap proper and ultimately have the data in OSM, but you cannot import questionable data just like that.