The local consumer office could be your first call (take someone who speaks spanish with you) Not sure where this development is but there are some recommended lawyers on this site from all areas.
Read all Charlie’s (Barbara) posts. She and a group of others successfully won a case against a developer and i’m sure joint action is the cheapest and strongest way to go. If you PM her, sure she would point you on the best way to start (or Claire).
It sounds as though the third block they have added later could be illegal, best to act quickly before people actually complete and then it could possibly be demolished.