I choose I would rather be fluent in all languages. The reason is quite simple. Human are social animals, such implies, for survival, we have to communicate each other verbally or non-verbally, in such a way that the message you want to deliver is well understood by the receiver. Taking the essence of understanding, I simply regard that the world speaks tons of languages where as popularity and usefulness of a language depends on population and socio-economical status of a particular language. Take English as an example, we regards English to be the universal language because it influence a lot of sectors in our daily life also because of the economic status of the countries that use English as a native or official language. Not to mention that English has a lot of variation according to the geographic and politic aspect of a country. Inversely thinking, imagine that you are in China and all the languages you have every learnt was English and your native, what could possibly you could do. You could find someone who knows and speak your native or English or maybe use the advantage of technology, use a translator app which solely translate and interpret based on a model. Now, here come the clutch, the way most language works can be covered with language models is not accurately depicted which means not fully correct, and there are a tons of language features which is so subtle that a math based language model can not comprehend. The thing is that many language adopt quirky nuances in creating new words, jargons and trends. The best is you can understand the base meaning yet you can not fully comprehend the essence of the sentence. Thus why I choose to be fluent in every languages.
To conclude, I think if you want to survive and thrive in today's world of globalization, you would achieve almost everything if you are fluent in all languages to be exist.
