How to backup my files without Permission / Ownership?

Hi there. I have been running win 7 for many years without issues. Finally upgraded to Win 10. Things were fine for about a month, suddenly after a normal restart Windows 10 just stopped working. No Taskbar, Startmenu, Keyboard, Internet and most Win 10 Services not working. Biggest Issue is that I am sudenly not able to backup my very own files. I do not have permission anymore. I have tried many many ways in order to backup my files but I am not allowed to view, copy or move them. Not in Win 10 and not via Knoppix. How can I get my files back? I managed to move them to an external HD but as I just mentioned I cant view them, neither copy or move them any further. How can I get my files back? I am the Admin, I can see the files and the sizes but unable to play copy and use them. I tried gksudo nautilus, nothing works - I am stuck! Any help would be greatly appreciated!

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Biggest Issue is that I am sudenly not able to backup my very own files..
I managed to move them to an external HD but as I just mentioned I cant view them, neither copy or move them any further. How can I get my files back?

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I don't understand. You moved your "very own files" to "an external HD", but you cannot see them on the external HD? How do you know, "move" has been successfull?