unsigned long oldTime1 = 0;

int leds[] = {2, 3, 4, 5};
int btt1 = 10;
int btt2 = 11;

int speed = 1000;
int disabledLeds = 0;

void setup() {
  for (int i = 0; i < 4; i++) {
    pinMode(leds[i], OUTPUT);
  }
  pinMode(btt1, INPUT_PULLUP);
  pinMode(btt2, INPUT_PULLUP);
}

void loop() {
  if (millis() - oldTime1 >= speed) {
    for (int i = 0; i < 4; i++) {
      if (i >= disabledLeds) {
        digitalWrite(leds[i], !digitalRead(leds[i]));
      }
    }
    oldTime1 = millis();
  }

  if (digitalRead(btt1) == LOW) {
    if (speed > 500) {
      speed -= 500;
    }
    delay(200);
  }

  if (digitalRead(btt2) == LOW) {
    if (disabledLeds < 4) {
      digitalWrite(leds[disabledLeds], LOW);
      disabledLeds++;
    } else {
      for (int i = 0; i < 4; i++) {
        digitalWrite(leds[i], HIGH);
      }
      disabledLeds = 0;
    }
    delay(200);
  }
}