Bluetooth Control Car

int motor1Pin1 = 5; 
int motor1Pin2 = 9; 
int enable1Pin = 6; 
int motor2Pin1 = 8; 
int motor2Pin2 = 10; 
int enable2Pin = 11; 
int state;
int flag=0;        
int stateStop=0;
void setup() {
    // sets the pins as outputs:
    pinMode(motor1Pin1, OUTPUT);
    pinMode(motor1Pin2, OUTPUT);
    pinMode(enable1Pin, OUTPUT);
    pinMode(motor2Pin1, OUTPUT);
    pinMode(motor2Pin2, OUTPUT);
    pinMode(enable2Pin, OUTPUT);
    
    digitalWrite(enable1Pin, HIGH);
    digitalWrite(enable2Pin, HIGH);
    
    Serial.begin(9600);
}

void loop() {
    
    if(Serial.available() > 0){     
      state = Serial.read();   
      flag=0;
    }   
    // if the state is '1' the DC motor will go forward
    if (state == '1') {
        digitalWrite(motor1Pin1, HIGH);
        digitalWrite(motor1Pin2, LOW); 
        digitalWrite(motor2Pin1, LOW);
        digitalWrite(motor2Pin2, HIGH);
        if(flag == 0){
          Serial.println("Go Forward!");
          flag=1;
        }
    }
    
    // if the state is '2' the motor will turn RIGHT
    else if (state == '2') {
        digitalWrite(motor1Pin1, HIGH); 
        digitalWrite(motor1Pin2, LOW); 
        digitalWrite(motor2Pin1, LOW);
        digitalWrite(motor2Pin2, LOW);
        if(flag == 0){
          Serial.println("Turn RIGHT");
          flag=1;
        }
        delay(1500);
        state=3;
        stateStop=1;
    }
    // if the state is '3' the motor will Stop
    else if (state == '3' || stateStop == 1) {
        digitalWrite(motor1Pin1, LOW); 
        digitalWrite(motor1Pin2, LOW); 
        digitalWrite(motor2Pin1, LOW);
        digitalWrite(motor2Pin2, LOW);
        if(flag == 0){
          Serial.println("STOP!");
          flag=1;
        }
        stateStop=0;
    }
    // if the state is '4' the motor will turn LEFT
    else if (state == '4') {
        digitalWrite(motor1Pin1, LOW); 
        digitalWrite(motor1Pin2, LOW); 
        digitalWrite(motor2Pin1, HIGH);
        digitalWrite(motor2Pin2, LOW);
        if(flag == 0){
          Serial.println("Turn LEFT");
          flag=1;
        }
        delay(1500);
        state=3;
        stateStop=1;
    }
    // if the state is '5' the motor will Reverse
    else if (state == '5') {
        digitalWrite(motor1Pin1, LOW); 
        digitalWrite(motor1Pin2, HIGH);
        digitalWrite(motor2Pin1, HIGH);
        digitalWrite(motor2Pin2, LOW);
        if(flag == 0){
          Serial.println("Reverse!");
          flag=1;
        }
    }
    
}