Hello, Imad,
Thank you very much for your great article! Yesterday I also published an article about COVID-19 from a data science perspective. There I wrote why representative studies are important. I looked for representative studies and found something. With this data I calculated the lethality and I also calculated with autopsy results how many of the people who were officially listed as COVID-19-dead, actually died of COVID-19. From these results it could then be calculated how many people were probably already infected with COVID-19 in Germany or are already infected. Maybe this article is also interesting for you.