Hi Fernanda,
So to remove duplicates, I'd recommend a workflow with a query activity leading into a dedupe activity that splits the duplicate records into a compliment. From there you can have that outbound transition lead into an update data activity. It is within this activity that you can choose to delete these records. Please see the documentation below:
https://docs.adobe.com/content/help/en/campaign-standard/using/managing-processes-and-data/data-mana...
Of course when talking the deletion of data, I'd recommend doing some test runs in your Stage environment, then doing a test run in Production just on a single record before doing any mass delete.
Regards,
Craig