Automatic repair loop in bootcamp

Hi all!

After searching for hours on google and here trying to find a solution Im writing here for your help or ideas on how to fix this problem.

I have imac 5K with windows 10 installed. Everything was working just great. Last night windows installed an automatic update and the nightmare began. After restarting my computer Windows 10 went to " Preparing automatic repair" after awhile a blue screen shows with windows options from which none seem to work.

Now the only thing that happens is that every time I restart Windows 10 it goes to "Preparing automatic repair" , after that a black screen and then the blue screen with Windows options ( Troubleshoot, Use a device, Continue to windows and Turn off your PC) Which none seem to do anything.

I dont want to lose important data on my Windows drive. And yes I am open to installing Windows all over again but without losing the data.

Yes I have a usb with Windows installed. I tried booting from it but I can´t seem to get to the Repair Windows option.

All the help is welcomed.