Thanks for the tip.
However, when I tried to install unrar in the terminal I found out that I already have it.
I then tried this: I right-clicked on the first rar file (number 0) and chose "open with archive manager" (the alternative on the top). Then a pop-up window appeared with the whole movie as one piece. I right-clicked again and chose "open with VLC" and then could successfully watch the movie.
Stop worrying, start breathing!