Are you saying that your email account has been compromised and the hacker has full access to that email account? If so the first thing is to check out the email account and get the password changed.
If a hacker has deleted emails from the Trash folder of the Webmail mailbox then unless you have copies on another device those emails are permanently deleted and there's no backup facility available.
Are you able to sign in to your email account mailbox via the Webmail TalkTalk Mail sign in? If you can then you can check out your email account for suspicious activity to see what emails are there. Check to make sure there's no email forwarding been set up to any email account you don't recognise.
Password recovery may have been set up for the email address with an alternate email and or mobile number. Please do try the Reset your Password option. Other than the reset to the account itself, if there are alternates listed, see if you recognise them from the hints and if you do have access to the alternate email or mobile then please reset the password. If you only have access to the email account itself then have a password reset sent to the email account and change the password within 30 minutes.
Or if you're a TalkTalk broadband customer or recent customer you can change your email password in MyAccount > My Services > Webmail - Manage Webmail, if the email is listed in one of the 5 email address slots.
Here's the advice article on managing your email in MyAccount.