I'm sorry to say: You can't win against an attacker who has stolen your account. If the attacker has changed the account's username, password, MFA authentication and recovery information like your phone number - and unless your attacker is a complete amateur they did all that within the first minutes of the attack - you will never get your account back.
Instead, you need to worry about what mischief or worse the attacker can do with all the information about you in your account, which is now in their possession, and quickly take steps to protect your identity.