Programming an autonomous robot with Arduino Mega.

I have partially ready code, however I can't implement it in Arduino. The idea is to send coordinates to the arduino via WIFI and the robot to carry out the route autonomously. The robot's physical part is already ready, what I need is to program it so that when it reaches a geographic coordinate, it makes a decision to go ahead, turn right, or turn left. GPS sensors, Bussola, Ultrasson and Wifi module will be used. 3 Arduino pins will be used and when it reaches its waypoint it will connect these three Arduino pins. For example (HIGH,LOW,HIGH).