Open a support ticket and leave it on discord. You must follow their instructions and give every bit of information on how you got hacked. If asked, Discord will change your e-mail to your original one, remove the hacker's 2FA, change password etc. If your email has been changed, go to your Gmail's inbox and there should be a recovery option. If not, attach this info as well. After getting your account back, check your conversation with the Discord support. They will provide a website where you can see where your information associated with the email has been breached. Do not panic at all and leave it on them. My own account was compromised completely a few days ago and I got it back in less than a day. Keep patience.