It was unfortunate that I had to start again from scratch. However, I let myself to learn from it.
"No upgrade without having backup first."
I am trying to retrieve my old posts which of them I keep as notes.
I always choose "Joomla" over "Wordpress" because my learning of Web Content Management System (WCMS) has started with "Joomla".
I did use Wordpress for some of the websites I had developed even though Joomla is my first choice.
Ok, this time I will take more care to do regular back up.
Thank you for your time.