I suceeded in decrypting all files by the googled instructions. Thank you for reminding me of the encrypt issue.

most of files have a lock sign, but some can be opened and others can't be. why?

I guess it is the case. The folder originally created in another pc, and I don't know how to decrypt it, and how to remove the encryption on that machine, as I don't want such a sort of problem in...

Yes，the file is marked with all permissions.

The ownerships successfully changed, but I still can not open and copy the files.

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