Windows 10 updated but does not load any more

Hi. I have a Dell Laptop 7000 series. I bought it in April 2014 with Windows 8.1 on it. Soon I got a message that I can upgrade it for free to windows 10, which I did!
This morning I got a message that windows need to be updated and it takes a while. I clicked ok. It kept updating until iy became almost 80% complete. Then all of sudden I got a blue screen which says: Choose your keyboard, I did choose US keyboard. Next thing was another blue screen giving me 6 options:
1) Continue: Exit and Continue to Windows Roll back
2) Use a device: USB drive, Network connection, or windows recovery dvd
3) use another operating system : continue with another installed version of winmdows
4) troubleshoot : reset your pc or see advanced options
5) turn-off your pc
I do not know what is Windows Roll Back.
I have chosen options 1 and 3: on option 3 I went to option windows 10 grade 5!!!! but like option 1 i keep getting same issue: black background and an error message: C: windows\System32\config\systemprofile\Desktop is unavailable. If the is on this PC, make sure the device or drive is connected or the disk is inserted, and then try again. If the location is on a network, make sure you are connected to network or internet, and then tryagain. If the location still can't be found, it might have been moved or deleted. click OK.
As soon I click Ok, an empty black desktop shows with only a trash basket icon.
at the bottom corner it shows:
1) audio is disconnected ( which by trouble shooting works).
2) no internet connection. i even used cable and thought the issue is wireless, but dont work. When I click trouble shooting it gives an error while trouble shooting:
Package ID: Unknown, ;Path: Unknown; error code: 0x80070426; Source: Engine User: My computer name\my name ; Context: Restrickted.

on Option 1 sometimes i see for few minutes this pops up on my screen: >>> Start PXE over IPv4.

When I chose Statrt Up repair, it says it could not repair my pc., press advanced option, which i did but no help.

I appreciate your help. I have no backup of windows nor of my files and I need them. Thanks