Just to confirm, are you still able to sign into YouTube? If yes, we suggest adding extra layers of security to your account w/ these tips: https://yt.be/help/XEbn . Otherwise, try recovering your account by going through these steps: https://yt.be/help/nr5 . Keep us posted.
@TeamYouTube I can access to my email and add extra security to my email as your tip. But the problem is my channel on my accessed email is already transfered to another email address. So can you please return my channel to my email from that stealer.