Physiological studies have found that speaking two or more languages is a great asset to the cognitive process. The brains of bilingual people operate differently than single language speakers, and these differences offer several mental benefits.
Moreover speaking a foreign language improves the functionality of your brain by challenging it to recognize, negotiate meaning, and communicate in different language systems. This skill boosts your ability to negotiate meaning in other problem-solving tasks as well.
From my point of view, as a psychologist and a bilungual learner, each one of languages has different structures and words which express the same idea or thought. There are different idioms used around the world; these can sometimes help you find the root of some words or idioms of your own language, e.g.
All of that, and some things more, contrubutes positively your brain: connections are increased, and brain's health is more balanced or even is grown.