Garbled File Names & .txt file contents

1- Downloading a file -which has CJK name- through Safari, became garbled.

2- It doesn't matter which language it has, every .txt file I have in my macOS (except I created a txt file by myself), the content is garbled.

In this case, actually we had a solution by Apple which named "File Name Encoding Repair Utility" but since it is outdated, I cannot use it since Catalina. Please don't give me very basic solutions like "update your system, check your macOS location settings etc.", because I've tried almost everything and nothing solves this problem.

I really want to know the real and exact solution... The all Apple computers in China have this problem.

I give you three examples:

1- the file which has been download through Safari

2- an unzipped file

3- garbled txt