How can I copy the old data from iPhone 5 to iPhone X

Do an iCloud backup from the iPhone 5. Then restore the iPhone X using the same icloud backup.

Make sure you use the same Apple ID/iCloud account.

iCloud: Back up your iOS device to iCloud

iCloud: Restore or set up your iOS device from iCloud

https://support.apple.com/en-us/HT201269

Or use iTunes to do the backup. I feel more confident knowing that my data is right here :-)