Slow, and really, they cracked the language code that fast?

Rating: 5/10 (23 February 2017)

***SPOILERS SPOILERS***
Thank goodness I watched this at home and could take a break after the first hour--very slow moving, like your average glacier.
A major portion of the movie focuses on the effort to learn to communicate with the aliens who have landed on various parts of Earth. Within what appear to be weeks or months--let's assume months, even though it's never made clear--our heroine, language expert Dr. Louise Banks, has figured out how to communicate with the aliens, who seem to communicate with a few vague sounds and a lot of dynamic visual symbols. Louise and the aliens go from exchanging a few simple symbols (the written word for human, the alien expression for who they are, etc.). A man provides a demonstration of "walking." And the next thing we know, Louise is talking to the aliens in short sentences, which the aliens more or less understand. And we're not just talking "Boy eat apple"-type sentences. No, we're talking abstract concepts like "what is your purpose," "weapons," and so on.
I simply could not believe that they could crack the language code so quickly. Sorry.
Also, another key plot point of the movie is what appear to be Louise's flashbacks. We come to understand what these are by the end of the movie, but my, wasn't it convenient who and what she did and did not remember? And the timing of the flashbacks was peculiar. I could not buy that at some point during the entire "mission," she did not look at the other character and say, "Wait, I know you!" Very inconsistent and unbelievable.
While watching this movie I had a distinct feeling that it was based on a book. (It is in fact based on a short story.) Some stories are "mind" stories, internally focused as much as anything else, with much or most of the story impact deriving from the state of the protagonist as he/she is perceiving and interacting with external situations. Also, some stories rely on a certain unique written style to enhance the story impact. All of this was my sense about "Arrival"--that as a written story, it might have been quite intriguing from a mental/psychological and stylistic POV, but trying to transfer something like that to a visual medium like the big screen might have caused it to lose some of that impact. (I have not yet read the short story, so I could be wrong.) Anyway, JMO.