Monolingual societies suffer because of a lack of linguistic diversity. A second language adds another perspective to life and the journey provides plenty of failures and successes that eventually become funny memories. In short, learning a second language makes us better individually. The cumulative effects of a large number of individuals learning a second language would by extension benefit society.
Learning a language is a journey. Anyone who has tried to learn a foreign language will agree. I was relatively quiet so putting myself out there knowing I was making mistake was difficult. But this is the benefit of a foreign language. Once you get the hang of the basics, these mistakes fade. Once they do and your ability to communicate grows so too does your confidence. At least mine did anyway. Once this hump is cleared are the benefits of a foreign language truly unlocked because there is a whole new world to explore. Of course, this invites new experiences which may encourage you to challenge previously held beliefs. So to say that a second language can help you improve as a person is not an exaggeration.
Unfortunately learning a second language cannot exclusively be learned from a textbook. You need to embrace the target language. Read books, listen to music and watch TV and film in the language. This will improve listening and understanding but it needs to be put into practice. It takes effort to learn a language but it is worth it.