"Impossible to create the root directory "/var/www/html/mygigstar-admin/code/code/php/storage/app/public/image". " code example
Example: laravel impossible to create the root directory
This link has an answer that has worked for many users.
It is bound to work for you too!
https://laracasts.com/discuss/channels/general-discussion/impossible-to-create-the-root-directory-error-when-uploading-file-into-public-folder