There are two sets of global keys for Safari browser: the one for Mac OS X and the one for Windows operating system. The latest version of Safari for Windows is 5.1.7. It seems apple skipped the update and now there is only one version, the one for Mac OS X.
However, on Windows use ALT for Option and Windows key for Command, then simply browse to the following website to see all the available commands. Replace the commands as instructed and it should function normally.
Support page: https://support.apple.com/en-gb/HT201236