I am not sure how my Yoga 2 13" running on Win10 got into this terrible problem.

It boots up and shows up the login screen as usual. But when I enter the password and login, it takes ages (~30 min) to loads the desktop and its icons and remains extremely slow. Sometimes it never loads. It shows a black wallpaper, busy mouse pointer and the task bar but nothing functional.

I tried these-
1. BIOS boot mode UEFI & Legacy - Issue exists on both.
2. Startup repair - Didn't work.
3. System restore - Unknown error.
4. Factory reset (by keeping personal files) - Failing in between.
5. Safe mode - Same issue.
6. "sfc /scannow" on Safe mode with Command prompt - Windows Resource Protection found corrupt files but was unable to fix some of them.

I have important files that I dont want to loose for obvious. Can some please help me rectify this?