A "global language" is by definition a language learned by significant numbers of people as a second language [1].
By most people's accounting, only English, French, and Spanish are global languages. "Minor" global languages on the rise include Mandarin, Arabic, and Hindi, but these do not have nearly the geographical distribution nor the populations of second language learners that the main global languages have.
That said, unless you have a partner or other significant connections to your target language community, consume a large amount of target language media, or are living in a country that speaks your target language, speaking to other people is not the main motivation to learn a language. You learn a foreign language because it's fun and because there are numerous studies indicating knowing a foreign language benefits your mental abilities and health.