Good evening
I need your help. it works I have a squeak in the Z but I am going to revise it. I managed to make a drawing that seems good to me for the first time probably adjustments to improve. can’t manage to do the Home setting each time the Z goes up and X and Y go to a corner and forcefully, I would like to be able to determine a starting point on the machine but I don’t see how.
thank you for helping me
As far as I know, you need to use some sort of CNC controller software (e.g. Universal Gcode Sender, cncjs, etc.), use its controls to jog your machine to the spot where you want to set the zero to, and then set it there also from the controller software.
I don’t have a MPCNC yet though! I’m currently printing, but I have some experience with other CNC machines (i.e. 3D printers, pen plotters, etc.). 
The Home command assumes switches (or other sensors) are in place at one end of each axis’s limit of travel and the behavior you are seeing is the machine attempting to hit those switches.
If you don’t have end-stop or limit switches, then you manually jog the tool to the desired starting location and send a G92 X0 Y0 Z0 to reset the machine’s origin to the current position. The menus or touch-screens often have a button dedicated to sending this command, but as I run a different controller than most folks on these forums I can’t steer you to the right one for your machine.
Details on G92 can be found in this Marlin command documentation.
If you have a Z touch-plate, use G92 X0 Y0 first, then complete your Z probe routine to set the Z position.