Hi there marslaw1002,
Thanks for joining us in Apple Support Communities! We understand your Mac is getting stuck while moving or copying files to your external hard drive. We're glad you're here, and we can provide some guidance.
To start, check the permission settings with the steps here:
If you can’t move or copy an item on Mac
If that doesn't seem to help, try the suggestions in this link:
If your Mac runs slowly
If the issue persists, let's use Disk Utility to verify and fix any issues with your drives. This link provides step-by-step instructions:
Repair a storage device in Disk Utility on Mac
Let us know how it goes.
Cheers.