I understand you are not able to use FaceTime because there is an issue with your Apple ID, is that right?
The first step is to edit / update your Apple ID (which is an email address). The resources below will explain how to find your Apple ID, change it if necessary, reset the password, etc. I'll also include a link to the Apple ID Support team to help you get this straightened out.
Learn how to change the email address that you use as your Apple ID.
In most cases, your Apple ID is also the primary email address of your Apple ID account. You can change your Apple ID to any other email address you control, as long as it's not already in use as an Apple ID. If your email address ends with @icloud.com, @me.com, or @mac.com, it's already an Apple ID.
Use these steps to reset your Apple ID:
Sign out of iCloud, the iTunes Store, App Store, FaceTime, Find My Friends, Find My iPhone, and iMessage on each device that uses your current Apple ID for these services.
When the My Apple ID page opens, sign in with your new Apple ID email address and password. When you see a message that verification is complete, you can start using your updated Apple ID.
Your Apple ID is the account you use for everything you do with Apple: shopping the iTunes Store, signing in to iCloud, buying an app, using iMessage, and more. We recommend that you use the same Apple ID for all Apple features and services. If you want to change the email address associated with your Apple ID, sign in to My Apple ID to change your email address, then use these steps to update it in the services on your device.
FaceTime
Tap Settings > FaceTime.
Tap your Apple ID, then tap Sign Out.
Tap Use your Apple ID for FaceTime.
Enter your Apple ID and password, then tap Sign In.