Throughout the Marvel films, and to some extent the comics as well, we see lots of different species of creature all communicating in the same language, English (for the English version of everything) except for Groot.
Previous answers have covered both the Asgardians (their language is understood by all and they understand all) and specifically Star Lord, he has a translator in his neck.
But how does this work for characters who don't have a translator for instance the humans of Earth who are not Star Lord are able to easily understand non human, non Asgardian characters with no effort?