How to make a duty cycle using 2 LEDs using arduino?

I want to make a duty cycle of 2 LEDs using Arduino in tinkercad. I have 2 LEDs 1 is red and another is green. I want both the LEDs on at the same time but a glowing delay of red led is 1second and green led is 1.3second just like the graph below and having both duty cycle 50%.

but I cant be able to do that I had tried with 2 blocks of if-else but it doesn't work due to its take if-else synchronously then I tried to calculate the graph and want to put it as a delay but it is not an easy solution

I've learned about millis() is the solution but how would I use it? Please help me to solve this problem

Try this code:

#define LED11_PIN 11
#define LED12_PIN 12
#define LED12_BLINK_RATE 1000
#define LED11_BLINK_RATE 1300

class Led
{
  private:
  bool _ledState;
  const int _ledBlinkRate;
  double _lastStateChange;
  const int _ledPin;
  
  public:
  
  Led(int blinkRate, int ledPin) : _ledState(false),_ledBlinkRate(blinkRate), _lastStateChange(millis()), _ledPin(ledPin)
  {}
  ~Led()
  {}
  void update()
  {
    double currTime = millis();
    if((_lastStateChange + _ledBlinkRate/2) <= currTime)
    {
      _ledState = !_ledState;
      
      digitalWrite(_ledPin, _ledState);
      
      _lastStateChange = currTime;
    }
  }
  
  
};

Led led11(LED11_BLINK_RATE,LED11_PIN);
Led led12(LED12_BLINK_RATE,LED12_PIN);

void setup()
{
  pinMode(LED12_PIN, OUTPUT);
  pinMode(LED11_PIN, OUTPUT);

}

void loop()
{
    led11.update();
    led12.update();
}