Hi Sergio
Via the documentation, you can find your way on how to expose your datamodel via OData v3/v4 the correct way: https://docs.mendix.com/refguide/integration/odata-services/
If you want to make (parts of) your datamodel available through OData, you can follow the instructions here: https://docs.mendix.com/refguide/published-odata-services/
To check which entities are readable go via https://docs.mendix.com/refguide/published-odata-entity/#readable
To fetch your association, you can find a detailed how-to here: https://docs.mendix.com/refguide/supported-odata-operations/, below 2.3 Retrieving associated objects: https://docs.mendix.com/refguide/supported-odata-operations/#231-retrieving-associated-objects
I hope this helps you further.
Kind regards,
Leander
Thanks for your help, it was very useful!