These Steps UninstallWindows 10to Back Windows 7 or Windows 8.1. Use the settings to Going back Windows 7 or Windows 8.1 from Windows 10
If it’s been less than a month since you upgraded to Windows 10, you can go back to your previous version of Windows by going to Settings > Aktualisieren & Sicherheit > Recovery and selecting either Go back to Windows 7 or Go back to Windows 8.1. This won’t affect your personal files, but it will remove any apps you installed after the upgrade to Windows 10.
If it’s been more than a month, this option won’t be available in Settings and you’ll need to use adifferent recovery option.