Converting Arduino MEGA Code to Arduino DUE Code?

I've been working with MEGA before. This code works completely with MEGA. I'm still at beginner level in Arduino, how do I adapt this code to DUE?I'm asking this question because I think the only problem in adaptation seems to be SoftwareSerial.

#include <SoftwareSerial.h>
SoftwareSerial bluetooth(52,53);    // TX,RX                               
int bar_analog=0;                                    
int head_analog=0;
int bar_anim=0;
int strip_anim=0;
int motor_speed=1;
int direct=0;
int level=0;
boolean debug = true;
int IN1a=49;
int IN2a=48;
int PWM1=3;
int IN1b=22;
int IN2b=23;
int PWM2=4;
int hiz=100;
int PWM_kare=2;
int INA_kare = 51;  
int INB_kare = 50; //LED '+'sı OUTPUT B'de olduğu için INB'yi  HIGH yapıyoruz.
void m1_cw() {
digitalWrite(IN1a,HIGH);
digitalWrite(IN2a,LOW);
analogWrite(PWM1,hiz);
}
void m1_ccw() {
digitalWrite(IN1a,LOW);
digitalWrite(IN2a,HIGH);
analogWrite(PWM1,hiz);
}
void m2_cw() {
digitalWrite(IN1b,HIGH);
digitalWrite(IN2b,LOW);
analogWrite(PWM2,hiz);
}
void m2_ccw() {
digitalWrite(IN1b,LOW);
digitalWrite(IN2b,HIGH);
analogWrite(PWM2,hiz);
}
void m1_stop() {
digitalWrite(IN1a,LOW);
digitalWrite(IN2a,LOW);
analogWrite(PWM1,0);
}
void m2_stop() {
digitalWrite(IN1b,LOW);
digitalWrite(IN2b,LOW);
analogWrite(PWM2,0);
}
void mast_up() {
digitalWrite(24,HIGH);
digitalWrite(25,LOW);
}
void mast_down() {
digitalWrite(24,LOW);
digitalWrite(25,HIGH);
}
void mast_stop() {
digitalWrite(24,LOW);
digitalWrite(25,LOW);
}
void kare() {
analogWrite(PWM_kare,head_analog);
digitalWrite(INB_kare, HIGH);
digitalWrite(INA_kare, LOW);
}
void setup() {
  Serial.begin(9600);                              
  bluetooth.begin(9600);                           
  Serial.println("Program is starting...");              
  Serial.println("by Berke Ogulcan Parlak"); 
pinMode(IN1a,OUTPUT);
pinMode(IN2a,OUTPUT);
pinMode(IN1b,OUTPUT);
pinMode(IN2b,OUTPUT);
pinMode(PWM1,OUTPUT);
pinMode(PWM2,OUTPUT);
pinMode(24,OUTPUT);
pinMode(25,OUTPUT);
pinMode(INA_kare, OUTPUT);
pinMode(INB_kare, OUTPUT);
pinMode(PWM_kare, OUTPUT);
digitalWrite(IN1a,LOW);
digitalWrite(IN2a,LOW);
digitalWrite(IN1b,LOW);
digitalWrite(IN2b,LOW);
digitalWrite(PWM1,LOW);
digitalWrite(PWM2,LOW);  
digitalWrite(24,LOW);
digitalWrite(25,LOW);
digitalWrite(INA_kare, LOW);
digitalWrite(INB_kare, LOW);
digitalWrite(PWM_kare, LOW); 
}

void loop() {
  if (bluetooth.available()) {
  while (bluetooth.available())                    
    {                                                //AppInventor'dan çektiğimiz verileri,değişkenlere atıyoruz.
      bar_analog = bluetooth.parseInt();              
      head_analog = bluetooth.parseInt();
      bar_anim = bluetooth.parseInt();
      strip_anim = bluetooth.parseInt();
      motor_speed = bluetooth.parseInt();
      direct = bluetooth.parseInt();
      level = bluetooth.parseInt();
      if (debug) {                                   // Arduin seri ekranından değerleri okumak için gereklidir.
        Serial.print("Bar Brightness: ");                        
        Serial.println(bar_analog);
        Serial.print("Bar Animation Type: ");
        Serial.println(bar_anim);
        Serial.print("Headlight Brightness: ");
        Serial.println(head_analog);
        Serial.print("Strip Animation Type: ");
        Serial.println(strip_anim);
        Serial.print("Motor Speed Level: ");
        Serial.println(motor_speed);
        Serial.print("Direction: ");
        Serial.println(direct);
        Serial.print("Mast Goes: ");
        Serial.println(level);
        Serial.println("--------------------------------");
      }
      if (bluetooth.read() == '\n') {               //Yazdırma işlemleri bu satırda yapılacak..
      
      }
  }}
  if(direct==1) { //ileri
  m1_ccw();
  m2_ccw(); 
  }
else if(direct==2) { //geri
  m1_cw();
  m2_cw(); 
  }
else if(direct==3) { //sol
  m1_ccw();
  m2_cw(); 
  }
else if(direct==4) { //sağ
  m1_cw();
  m2_ccw(); 
  }
else if(direct==0) { //durur
  m1_stop();
  m2_stop(); 
  }
if(level==1) { //mast yukarı
  mast_up(); 
  }
else if(level==2) { //mast aşağı
  mast_down(); 
  }
else if(level==0) { //mast durur
  mast_stop(); 
  }
kare();            //kare LED aktif.
  
















  
  }

So you were using software serial on the Mega, right?

Why?

Both the Mega and Due have four hardware serial ports and they map directly to the same pins. Time to port your code properly, as you should have done with the Mega. Or, just go back to the Mega and do it right as you certainly don’t need a Due to run that program. Other than having 3.3 volt I/O, the Due provides no benefit.