As you can see, Hernan Cortes is able to communicate with the Aztecs even when he has no clue about their language.
How were they able to communicate you ask? It is because of this woman. Her name Is Malintzin. She may be a slave but she plays a humungous role! She was a part of the Aztecs and so, she knew their language, Náhuatl. She also had to know Spanish, the language Hernan knows, otherwise she wouldn't be able to work for Hernan. So, she was able to act as a tranlsater since she knew both languages.
Therefore, they were able to communicate with the Aztecs and sort things out with each other. But eventually, it did lead for the Spanish to take over the Aztecs
But they were still able to communicate with each other and be able to sort things out. And even though when the Aztecs and Hernan knew nothing about eachother's languages...
They were able to find someone who was able to supervise the discussion and sort out any complications.