It's really not that easy to lose data...
if you rollback the update, you might lose some latest installed program...
Things can go south if you install new operating system on the wrong partition...if you get to a point where you have 2 OS on same partition, one that was installed b4 is moved to WINDOWS.OLD folder, that also contains some non OS files...
Just in case do an external backup...
And when all is fixed disable windows update service through services.msc
Don't do this. Not the correct way to rollback to previous version of Windows.
If you do indeed wish to rollback to W7, here is a guide http://www.thewindowsclub.com/rollback-from-windows-10
Once you are back at W7, the best way to prevent upgrade to W10 is via a tool like
Never10 - https://www.grc.com/never10.htm
W10 is more efficient than W7, and starts and runs better with fewer resources. It is however a bit of a snoop. However these spying features can be disable using tools like the ones discussed here
https://www.ghacks.net/2015/08/14/comparison-of-windows-10-privacy-tools/