proplem with serial connection

hi
whats problem in this code

//robot voice command via android
#include <SoftwareSerial.h>
const int led=13;
const int led1 =12;
SoftwareSerial BT(10,11);String voice;
void setup() {
BT.begin(9600);Serial.begin(9600);pinMode(led,OUTPUT);pinMode(led1,OUTPUT);
// put your setup code here, to run once:

}

void loop() {while( BT.available()){delay(100);
char c;
c=BT.read();
voice+=c;
{Serial.print(voice);
if (voice==“stop”){
digitalWrite(led,HIGH);
delay(500);

}
else if(voice==“start”){digitalWrite(led,LOW);
delay(500);

// put your main code here, to run repeatedly:

}}}}
when i send stop to arduino the led is start but when i send start the arduino isnot responce
plese help me and thanks

#include <SoftwareSerial.h>
const int led = 13;
const int led1 = 12;
SoftwareSerial BT(10, 11); 
String voice;
void setup() {
  BT.begin(9600); 
  Serial.begin(9600); 
  pinMode(led, OUTPUT); 
  pinMode(led1, OUTPUT);
  // put your setup code here, to run once:

}

void loop() {
  while ( BT.available()) {
    delay(100);
    char c;
    c = BT.read();
    voice += c;
    { 
      Serial.print(voice);
      if (voice == "stop") {
        digitalWrite(led, HIGH);
        delay(500);

      }
      else if (voice == "start") {
        digitalWrite(led, LOW);
        delay(500);

        // put your main code here, to run repeatedly:

      }
    }
  }
}

I can recommend use of the auto-format tool (ctrl-T) in the IDE.

Why don’t you reset “voice” when you’ve finished with it?

    char c;
    c = BT.read();

Why use two lines to do one line's job?

    char c = BT.read();