How do you think Europeans managed to understand abiriginal people everywhere they colonized?
Well sure, learning a distinct human language without an intermediary one has been done tons of times in human history... However, the big question with extraterrestrials is, "how do they communicate?". There's no reason they wouldn't use something other than forcing air through a flexible aperture in order to communicate with each other. As the article only briefly touches on, we have no idea how 'necessary' what we think of as language would be for other complex organisms/civilizations.
Of course. One example is very well described in the short story by Ted Chiang, on which Arrival is based. It's a fascinating story and well worth a read, whether you are interested in linguistics or not.
And it's not said we could communicate with aliens, it all depends if we are able to perceive their language.
All I'm saying is that the fact two people don't share a common language doesn't mean they can't learn each other's language. That was more an answer to the question asked in the sibtitle of this article than really adressing the hypothetical meeting with aliens.