help me choose my fifth language
edit: Thanks for all the comments! After reading through everything, I'm torn between Russian, Egyptian Arabic, and Japanese. Which one do you think is the best, and why?
Hi everyone, I'd love your input. My current levels are: Spanish (native), English (C2), Romanian (C1), and Norwegian (C1), learned in that exact order. I'm not looking for a language I can breeze through. What I really want is something that unlocks a whole new world of literature and cinema for me, so I can make the most of my free time. Since I don't have an external reason to learn another language (like moving to another country) I'll learn my fifth language just for fun. Given my background, which language would you pick, and why?