English. Most of Europe has English speakers particularly in business.
Chinese. Most of Asia bar Japan has Chinese speakers and they are often the business men too. Very hard to learn for a non-native speaker to become business fluent.
Spanish. This will cover a lot of South America and some parts of Africa.
If you can speak all those you will be able to communicate with probably 80% plus of humanity as a first or second language.
But if you want to work in Japan or France you will have to probably learn the local language...same for a lot of former Empire countries.
Bookmarks