If you get permission denied when you are trying to edit, delete or add a file in SFTP application like Filezilla for the website which is Hosting on Google cloud, you should open you can do following steps to solve the problem :

1- Open SSH in browser window in your Google cloud dashboard  :

Left side Dashboard -> Compute -> Compute Engine -> VM instances -> SSH -> Open in browser window

2- Then type following command line by line and press Enter to First add your username SFTP username to the group www-data then assign group www-data as an owner and finally grant permission to the www folder.

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