Hi, I'm Elise, a fellow user like yourself and I'd be happy to help with your issue.
Do you have any antivirus or security software running, as this can often be the cause of slow file transfers.
Window is also sometimes quite inefficient when copying large volumes of small files, rather than a small volume of large files.
It is also often quicker to use the robocopy app, you run this from the command line.
An example of copying from the C: to D: drive using this would be:
robocopy C:\ D:\ /E /COPYALL
Please let me know if you need any further assistance.
Kind Regards,
Elise