void setup() {
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
}
void loop() {
 // speed 0-255
  //1.forward---------
  analogWrite(5, 100);//speed 200
  digitalWrite(2, LOW);
  digitalWrite(3, HIGH);
  
  delay(5000);//5sec
  //1.forward---------
  
  //2.back-----------
  analogWrite(5, 100);//speed 100
  digitalWrite(2, HIGH);
  digitalWrite(3, LOW);
  
  delay(3000);//3sec
  //2.back-----------
  
  //3.forward-------
  analogWrite(5, 200);//speed 200
  digitalWrite(2, LOW);
  digitalWrite(3, HIGH);
  
  delay(5000);//5sec
  //3.forward-------
  
  //4.....
  

}