There are only positives for learning multiple languages.
Here is an arrangement of a few benefits from my vantage point.
Learning two or more languages offers people, children in particular, flexible thinking skills and strategies. Knowing there are other humans speaking many different languages around the world opens our minds to a tangible feeling of global connectedness. Flexible thinking broadens our acceptance of big ideas in all areas of human interaction.
Close to flexible cognitive skills is flexibility within social interactions. Once we know we are capable of learning another language are eager to learn more. Humans everywhere are creative around the globe having created over 6000 oral languages throughout our short history on Earth. The most common today are Mandarin Chinese, Spanish, English, Hindi, Arabic, Portuguese, Bengali and Russian. When we meet others we will be open hearted and happy to try to communicate with a smile and new vocabulary. It isn’t hard to do!
Becoming bilingual enhances our memory, our cognitive connections and enables us to have more and better communication.
Learning another language is similar to learning a musical instrument , using mathematical formulas, physics, chemistry . . . Deep mastery learning takes patient disciplined practice and usage. Deep meaningful learning engages our full attention and becomes a part of the person we are and the person we become.
The first time I saw ASL (American Sign Language) it was being used to interpret a song. I was hooked. I knew it was a kinesthetic addition to make learning comprehensible. I have used it ever since although I am still a beginner. My first experience with Spanish was with Senora Brown in third grade. We learned the colors in Spanish with her. It was a thin introduction to Spanish but it remains vivid.
I continue to study. Bilingualism, why not? Porque? Por que no?