Documents Folder Files Not Showing

Hi
I don't know how to solve this mystery so hope someone can help please.

If I click into My Documents from my Windows 10 PC desktop shortcut and eg I go into my folder named Garden, then I can only see some of my files in that folder. However if I click on file explorer and then click the Garden folder there, then all the files I have saved show there and not just some of them. On File explorer I have my documents saved under the E Drive instead of C Drive ( was advised to do this by tech support who said C Drive should only be used for program files etc and not for general document storage) Not sure if this makes any difference?

It's a bit worrying because when I make a back up to my external portable drive then the backup only shows the My documents folder which has the partial files?