@MilkShake Got it to work using:

{
   module: "MMM-NotificationTrigger",
   config: {
     useWebhook:true,
	 triggers:[
	   {
	      trigger: "PLAY_SOUND",
		  fires: [
		    {
			fire: "USER_PRESENCE",
			payload: function(payload) {
                  return false
                }
			}
		  
	   ]
	 },
	 {
	    trigger: "OPEN_GATE",
		fires: [
		   {
		   fire: "OPENING_THE_GATE",
		   exec: "sudo python /home/pi/open_gate.py"
		   }
		]
	 },
   ]
  }
},