Solution for this topic

Please make sure you have set proper file permissions to WordPress files as described on the following pages.

https://codex.wordpress.org/Changing_File_Permissions

https://www.smashingmagazine.com/2014/05/proper-wordpress-filesystem-permissions-ownerships/

http://www.wpbeginner.com/beginners-guide/how-to-fix-file-and-folder-permissions-error-in-wordpress/