Ki o tsukenakereba narimasen yo (You must take care!)Nakareba narimasen = must/have toeg.Jiko shōkai wa Nihongo de nakereba narimasen. (Your self-introduction must be in Japanese.)Chichi wa shigoto no tame ni Yōroppa e ikanakareba narimasen. (My father has to go to Europe on business.)-don't have to, add -nakute mo ii desueg.Kyō owaranakute mo ii desu....