Google Account Recovery Problem After Hacker Changed My Security Information

I am writing because my Gmail account, shineau***@gmail.com, appears to have been hacked without my permission, and I have not been able to access it properly since March 9. An unknown phone number ending in 87 was added to my account, and I noticed that my security information had been changed without my knowledge.

I tried to change the verification code and even entered another email address, such as o**@gmail.com, during the recovery process, but I still have not been able to regain full and secure access to my original Gmail account. When I try to log in, I run into security and access problems, and I strongly suspect that someone else may currently have control of my account.

Before this incident, I had used the same password on other platforms such as Instagram and YouTube, so I believe my information may have been compromised there first, which then led to my Gmail account being taken over.

My clear expectation from Gmail support is that they help me quickly recover access to my hacked account, remove the unknown phone number ending in 87, review and correct all security settings that were changed without my permission, and thoroughly investigate this unauthorized access.

I request that my account be secured, that only my correct recovery information remain on the account, and that I be informed of the steps taken to protect and restore my account.