Second, learning another language, allows you to speak with locals in their own language. This facilitates communication and mutual comprehension. An added benefit is that learning another language generates plenty of good will. After all, you invest the time and energy to learn the language of the other party, thereby showing an interest in his/her culture. You also, courteously, do not impose on locals by requiring them to speak your language or an international language like English.
Third, not unimportantly, you broaden your horizon if you learn another language. In fact, learning another language gives you access to another culture, another way of thinking, a different way of approaching people.
Having learned eight languages (including Turkish, Turkmen, Russian and several other European languages) myself, I enjoy zapping between television channels and noting the divergence in the coverage of news items in different parts of the world. Equally surprising to me is sometimes the sense of superiority with which international channels claim to provide you with unbiased coverage. Having access to native sources from various countries, however, makes you realize how diverse the truth can be.
Fourth, by learning a language you learn how to structure your thoughts. Of course this does not necessarily mean learning a foreign language, but could also involve your native tongue. Still, learning a foreign language could be beneficial for the development of your native tongue as you become better aware of certain terms or constructions that you would otherwise have taken for granted. By the way, this can also help you to understand the difficulties that foreigners in your country have to learn your mother tongue. As a result you will become more tolerant towards their mistakes and perhaps even more inclined to support them.
All in all learning languages improves worldwide communication and therefore mutual comprehension on a global scale. Without exaggeration one could therefore state that learning languages helps to reduce conflicts and to promote international stability. Its benefits therefore reach well beyond the individual level.