Why there are no more chinese language, theme change and file manager after updated to Android 7?

[AC Question]

After I updated my Huawei Nova plus Android 6 to Android 7 :

1. The Chinese language in "Language & Input" is missing, cannot download chinese language.
2. No more theme selections, changes and download are available
3. File manager is missing, unable to transfer files and photos using OTG pendrive.