This has been known for centuries, “languages expand your brain”. [Or, as we say: “expand one’s horizon”.] New studies (University York at Toronto, Canada) have shown and proven that those who are at least bilingual in old age will show their first symptoms of Alzheimer and Dementia (if at all ) later than those with one single language. [Autres études: l’Université d’Édimbourg en Écosse, et une équipe indienne.]
There is also a correlation between widely traveling and thereby being exposed to other cultures and languages, and a healthier brain capacity.
Besides the scientific implications of knowledge of several languages, not just one or two, there is also a practical side of this. When traveling, one who can communicate with the locals in another country often finds better deals and pays less. [My own experiences.]
Language tools are many using the NET, Google Translate comes to mind. Try it and find that the bot programs doing the translations are not sufficient to hide bad grammar resulting in the language being translated from English. One still has to know that language well.