g28 is home all, I do not use that.
I place the head where I want it to start, reset the arduino. That is 0,0,0, that’s it, super easy. Milling doesn’t lend itself well to endstops unless you are using an jig and doing a production run or bit changes (then you need a touch off z home not an endstop). Learn it without endstops first, then if you really want them add them later. They really do complicate everything.