If you want to learn Greek in-person, there are various organizations that operate in Athens and give that opportunity.
The map below showcases data in Greek language, that were organized by ACCMR and can be found through their article, here.
Instructions:
You may either choose to see the map within the article (1) or open the map to a different tab/application (2)
Then collapse the option of items to see the full list of data.
If you see multiple similar organizations in the list, it may offer different services according to the age of interested users (adults, minors).
Click on one of the organizations to see more details and pinpointed on the map.