Do you work on staging or directly on my live store?

Whichever is safest for your setup. For email work we strongly prefer to reproduce and test on staging or with sandbox addresses so we never blast your real customers with test sends. If only live access is available, we test against catch-all/sandbox inboxes and disable customer-facing sends until the fix is confirmed. We never flip the live queue on until a clean test send and 250 OK are verified.