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/