@qiancsf don't install NodeBB as root. Create an unprivileged user to install and run NodeBB under.
You need to install git.
@cyuime which plugin?
If the plugin isn't ready for translation, that is just has hard-coded english text, you need to modify it a bit.
See this for full instructions: https://docs.nodebb.org/development/i18n/
If the plugin is ready for translation, then it will have a folder such as public/language where various language files are kept like this