Was there some sort of official translator assigned to these ambassadors or perhaps even couriers, and was there any event where wrong translations or lost in translation issues led to conflicts/hostilities?
The ancient (and medieval) worlds were well aware of neighbouring peoples and languages, so there were always plenty of translators and interpreters. Here are some previous questions that will hopefully help:
For the Classical world, here are two answers from /u/toldinstone and /u/mythoplokos.
Here we have /u/Tiako who quotes St. Augustine's discussing learning foreign languages.
Here is a post by /u/BRIStoneman where they discuss what a person living in Anglo-Saxon England would use to learn a foreign language.
In this answer /u/CoeurdeLionne discusses learning foreign languages in Britain during the early Norman period.
This answer by me discusses learning foreign languages in Muslim Spain and the Holy Land.
And if you'd like to learn more about non-European forms of education, /u/keyilan discusses Korean methods of learning foreign languages here.