Realistically, English is a universal language; it's the number one language for music and for communicating with the rest of the world.
“Two things are desired in order that intercourse may be had: First, that a minister or agent be allowed to reside at the capital. Second, that commerce between different countries be freely allowed.”
“The true teacher defends his pupils against his own personal influence. He inspires self-trust. He guides their eyes from himself to the spirit that quickens him. He will have no disciples.”