Before you do, have a look at this.
I did the zwave course (xiaomi -zigbee) and this solution is just better in all respects. It works, It’s inexpensive and It’s easy to setup.
The simplest way forward with this is to get a couple of Sonoff rf gateways, flash them with a simple micro usb (no soldering, no wiring, nothing ) and order 7 to 8 dollar motion and contact sensors from china. There’s a list of proven sensors.