system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU] How does everyone understand each other.

So how do asgardians, genetically modified rodents, human-alien abductees with 4th grade educations, tree people, frost giants, kree, thanks, humans and whoever else all manage to speak english perfectly? Not only that, but there have been cases of language barrier in the MCU (the russian guy in iron man 2) so this couldn't be an alternate reality with only one language.
gpt
Asgardians speak the language All-speak which allows every thing with sentience to understand them and likewise. Basically they are so advanced they figured out the root of all language. Probably that magic vs science thing Thor mentioned. 

Most cosmic beings like Silver Surfer/Galactus are mentally so far beyond us that all they need are a few words spoken and they can become fluent in a language. 

I believe Quill just uses a universal translator.