Aotearoa / New Zealand

So, as some of you might know, I manage a small/medium tourism business. As well as GM, I'm also the IT Manager (and Safety Manager, Training Manager, Head Barista, Chief Toilet Cleaner, etc etc. You get the idea...)

I know we've got some super clever people here, and I know just enough to get myself into trouble. So, in the interests of "why pay an expert to do something, when I can do it myself in 5x the time" I thought I might try to revamp our IT systems... So, I'm seeking advice.

Our setup is pretty simple: cat-6 right through the building, coming to a passive bay and then to a 16 port SMC Switch. That's hooked to an ASUS DSL-AC55U that provides our Wifi and incoming VDSL. That all seems to work just fine for us, so not looking to change too much there.

Computer-wise, we have four, and looking to add a fifth (laptop). There's also a small NAS that I have setup as backup destinations for a couple of important databases that live on one of the PCs. The PCs themselves all function pretty much independently, with a tiny bit of file sharing to what I call the "main" computer. Really that's just for convenience though. Important files live on our MS365 OneDrive/Sharepoint, so those can be accessed from multiple points. Email is through our web provider and works fine (no shared calendars though).

Finally, we get to the point(s): is it worth adding a small server or similar to host a file share, or is that not likely to add any value over OneDrive? What else could I do with a server that I can't do currently? I did run a headless media server for a few years at home, so I'm vaguely familiar with the concepts and SSH etc.

Then, email: I'd love to have shared calendars (particularly so I can get my work calendar on my phone) - if I shifted my email across to MS365 (presumably I can keep our domain?) then would that add that capability or add any other value?

Anyways, this is mostly a thought exercise at this point, as I sit here in the office on a Saturday, while it's sunny out and my kids and wife are out having fun lol. Thanks for listening!