Check out which languages are spoken today most widely. You can add multiple languages, to check how much of the world's popultaion you could have a conversation with.
The list is not complete. All numbers are estimates in millions and only the 100 most widely spoken is included. L1 speaker is someone who knows the language as good as a mother-thounge speaker, or is one (C2 level). L2 speaker is someone who has learnt the language, but knows it reasonably well (B1+ level)