This isn't really the right place for this, as Community Central is a site where you can discuss editing and administrating FANDOM wikis.
But to get to your point, it depends on a lot of factors, and may even be subjective. What language(s) do you speak now? Do you have any natural affinity with languages? How much knowledge of grammar do you have?
Generally, but not always, "easy to learn" are languages that are close to a language you already speak and use the same writing system. For Korean, that's both very far from English. If you put in the time and effort, you can learn anything. It won't come overnight, though. It's a long process.