Gmail Account Hacked Showing “Couldn’t Find This Account”

I have been using my Gmail account “muthamil040***@gmail.com” primarily on my Android phone. About one month ago I was still able to access it without any problems, but recently I received a notification and discovered that my account had been hacked. After this incident, my password appears to have been changed without my permission, and when I now try to sign in, Google shows the error “Couldn't find this account” as if the email address no longer exists. This situation is very worrying for me because this Gmail account is important for my personal use and other linked services. I have already tried all available recovery options, including “Forgot password” and the account recovery steps suggested by Google, but I have not been able to regain access or even get the account recognized again. I kindly request that my Gmail account be recovered if technically possible, that unauthorized access and changes be investigated, and that the security of my account and any linked services be ensured. I would also appreciate clear information about what happened to my account and what can be done to prevent similar incidents in the future.