PO files in multiple languages are loaded normally, but why are the menus garbled when you select Chinese?

PO files in multiple languages are loaded normally, but why are the menus garbled when you select Chinese? -- Debian information of the Linux release-the following is a detailed description. This media playback software runs in the Xorg environment and does not require KDE and Gnome.

The following is my language environment Configuration:

The zh_CN.po file header is as follows:
"Content-Type: text/plain; charset = UTF-8 \ n"
"Content-Transfer-Encoding: 8bit \ n"
"X-Poedit-Language: Chinese \ n"
"X-Poedit-Country: CHINA \ n"


Debian :~ # Locale-
C
POSIX
De_DE.utf8
Zh_CN.utf8

Debian :~ # Locale
LANG = zh_CN.UTF-8
LANGUAGE = zh_CN.UTF-8
LC_CTYPE = zh_CN.UTF-8
LC_NUMERIC = zh_CN.UTF-8
LC_TIME = zh_CN.UTF-8
LC_COLLATE = zh_CN.UTF-8
LC_MONETARY = zh_CN.UTF-8
LC_MESSAGES = zh_CN.UTF-8
LC_PAPER = zh_CN.UTF-8
LC_NAME = zh_CN.UTF-8
LC_ADDRESS = zh_CN.UTF-8
LC_TELEPHONE = zh_CN.UTF-8
LC_MEASUREMENT = zh_CN.UTF-8
LC_IDENTIFICATION = zh_CN.UTF-8
Lc_all= zh_CN.UTF-8


Note: If the following default locale is used, after the program is started, the menu appears in English, and you want to modify the language in the language settings, the result is only one option in English.
Debian :~ # Locale
LANG = C
LANGUAGE = C
LC_CTYPE = "C"
LC_NUMERIC = "C"
LC_TIME = "C"
LC_COLLATE = "C"
LC_MONETARY = "C"
LC_MESSAGES = "C"
LC_PAPER = "C"
LC_NAME = "C"
LC_ADDRESS = "C"
LC_TELEPHONE = "C"
LC_MEASUREMENT = "C"
LC_IDENTIFICATION = "C"
LC_ALL =

Check that my debian already has several Chinese character libraries, and the pathfont in xorg. conf loads the path of the relevant Chinese Character Library.

There are three more questions:
1. How does a PO File Load the font required?
2. Does KDE and GNOME in Xorg support Chinese characters?
3, UTF-8 need specialized Chinese font?


Thank you for your advice!
The English menu is displayed normally:

The German menu is displayed normally:

Garbled characters are displayed in the Chinese menu: