The top Chinese line says, “Messiah is Here!”
The second line's meaning isn't clear.
The third line says “Think truth, speak truth, do truth.”
The line below the flag is the Chinese translation of “Yechi adonenu….,” Chabad's declaration that the messiah is alive, well and is their rebbe – who died in 1994.
The second half appear to be the 7 Laws of Noah (Sheva Mitzvot Bnei Noach) that according to halakha (Jewish law) non-Jews are supposed to follow: