What does Word say the keyboard shortcut is for Save? (Open the file menu and see what the key combo is). It is ⌘S (Command-S) by default, so your Ctrl-S should be working. Is it showing something else, like ⌥S (Option-S/Alt-S) for you? If so, check to make sure you don't have a File->Save shortcut listed for ⌥S in your Keyboard App Shortcuts.
These App Shortcuts are another way to change keyboard shortcuts to your liking. I also use a PC keyboard, but have learned to use the default key mappings and Mac shortcuts. Ctrl=Control, Alt(ernate) is just another word for Option, and the Windows key looks similar to the Command (⌘) key. Just as an example, the screenshot below shows a keyboard shortcut for Word to use the (unmapped) Control/Ctrl key. This is specific to Word, but it could be done for All Applications instead.
On your Mac, assign your own shortcuts to menu commands in any app or in the Finder.
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