I suppose investing in English, Spanish or French, Russian, Arabic and Chinese gives you a global passport and a good basis to learn other languages. But the above combination would seem impossible. On the other hand if we were cured tomorrow, i would go for it. Challenges of the pre-t life was a walk in the park. "Στερνή μου γνώση, να σε είχα πρώτα."
English is the best of these to be a lingua Franca. French and Spanish are okay. Not really Russian but whatever. Fuck Arabic and Chinese (coming from someone who speaks a dialect of it). It's possible but very hard. I've learned so many languages and that's why I support a universal one. Doing this is just far too tedious.