Blinking bicycle light with LED

/*
Program to switch trough 4 program modes by pressing a simple push button. 
Mode 0 = All LEDs turned on
Mode 1 = Blinking LEDs. The LEDs are dividied into two groups. When one group is off, the other LED group is on and opposite.
Mode 2 = All LEDs are blinking fast at the same time.
Mode 3 = All LEDs turned off
  

  The circuit:
  - LED attached from pin 2, 3, 4, 5, 6, 7 to ground
  
  - pushbutton attached from pin 12 to +5V with 10kOhm in between to lower current
  

  created 03 May 2020
  by Thomas Wolters

*/
// constants won't change. They're used here to set pin numbers of button and LEDs:
const int buttonPin = 12;    // the number of the pushbutton pin
const int    ledPin2=  2;     // the number of the LED pin
const int   ledPin3 =  3;     // the number of the LED pin
const int   ledPin4 =  4;     // the number of the LED pin
const int   ledPin5 =  5;     // the number of the LED pin
const int   ledPin6 =  6;     // the number of the LED pin
const int   ledPin7 =  7;     // the number of the LED pin
//
enum ZUSTAENDE:byte {ON, Blink, Blink_fast,OFF};  //Definition of program modes
byte zustand = ON;
// Variables will change:
int  ledState;           // the current state of the output pin
int  ledState2;         // the current state of the output pin
byte buttonState;             // the current reading from the input pin
byte counter = 0;
byte lastcounter =0;
byte Mode = 0;
int  lastButtonState = LOW;// the previous reading from the input pin
// the following variables are unsigned longs because the time, measured in
// milliseconds, will quickly become a bigger number than can be stored in an int.
unsigned long lastDebounceTime = 0;  // the last time the output pin was toggled
unsigned long debounceDelay = 50;    // the debounce time; increase if the output flickers

const long interval = 150;           // interval at which to blink at mode 1 (milliseconds)
const long interval_1 = 150;           // interval at which to blink at mode 2 (milliseconds)
unsigned long previousMillis = 0;        // will store last time LED was updated          
void setup() {
  pinMode(buttonPin,INPUT);
  pinMode(ledPin2,  OUTPUT);
  pinMode(ledPin3,  OUTPUT);
  pinMode(ledPin4,  OUTPUT);
  pinMode(ledPin5,  OUTPUT);
  pinMode(ledPin6,  OUTPUT);
  pinMode(ledPin7,  OUTPUT);
 //set initial LED state
  digitalWrite(ledPin2, HIGH);
  digitalWrite(ledPin3, HIGH);
  digitalWrite(ledPin4, HIGH);
  digitalWrite(ledPin5, HIGH);
  digitalWrite(ledPin6, HIGH);
  digitalWrite(ledPin7, HIGH);
}
void loop() {
    // read the state of the switch into a local variable:
  int reading = digitalRead(buttonPin);
  // check to see if you just pressed the button
  // (i.e. the input went from LOW to HIGH), and you've waited long enough
  // since the last press to ignore any noise:

  // If the switch changed, due to noise or pressing:
  if (reading != lastButtonState) {
    // reset the debouncing timer
    lastDebounceTime = millis();
       }
  if ((millis() - lastDebounceTime) > debounceDelay) {
    // whatever the reading is at, it's been there for longer than the debounce
    // delay, so take it as the actual current state:
    // if the button state has changed:
    if (reading != buttonState) {
      buttonState = reading;
           // only toggle the LED if the new button state is HIGH
      if (buttonState == HIGH) {
  // hier die cases einfügen        ledState = !ledState;
                        counter = counter+1;
                        zustand = counter;
                        if (zustand ==4){
                          zustand =0;
                          }
                        }
    switch (zustand) {
      case ON:
           Mode = 0;
      break;
      case Blink:
           Mode = 1;
      break;
      case Blink_fast:
           Mode = 2;
      break;
         case OFF:
           Mode = 3;
      break;
        }
      }
    }
 if (counter == 4){
 counter =0;
   }
// Second Whattodo
  unsigned long currentMillis = millis();
    switch (Mode) {
      case 0: //Turn light ON
           
          digitalWrite(ledPin2,  HIGH);
          digitalWrite(ledPin3,  HIGH);
          digitalWrite(ledPin4,  HIGH);
          digitalWrite(ledPin5,  HIGH);
          digitalWrite(ledPin6,  HIGH);
          digitalWrite(ledPin7,  HIGH);
             break;
      case 1: //Turn BLINK
           if (currentMillis - previousMillis >= interval) {
    // save the last time you blinked the LED
    previousMillis = currentMillis;
      Serial.print("previousmillis is: ");
  Serial.println(previousMillis);
    Serial.print("currentmillis is: ");
  Serial.println(currentMillis);
    // if the LED is off turn it on and vice-versa:
    if (ledState == LOW) {
      ledState = HIGH;
      ledState2 = LOW;
    } else {
      ledState = LOW;
      ledState2 = HIGH;
    }
    // set the LED with the ledState of the variable:
   digitalWrite (ledPin2, ledState2); //Vorderlicht 1 40mA
   digitalWrite (ledPin3, ledState);  //Vorderlicht 2 40mA
   digitalWrite (ledPin4, ledState2); //Vorderlichter Seite 2xparallel 38mA
   digitalWrite (ledPin5, ledState);  //Rucklicht Haupt 40mA
   digitalWrite (ledPin6, ledState2);  //Rücklicht links 20mA
   digitalWrite (ledPin7, ledState);  //Rücklicht rechts 20mA
    }   
         break;
      case 2: //BlinkFast
 //  unsigned long currentMillis = millis();
          if (currentMillis - previousMillis >= interval_1) {
    // save the last time you blinked the LED
    previousMillis = currentMillis;
    // if the LED is off turn it on and vice-versa:
    if (ledState == LOW) {
      ledState = HIGH;
    } else {
      ledState = LOW;
    }
    // set the LED with the ledState of the variable:
    digitalWrite (ledPin2, ledState);
   digitalWrite (ledPin3,  ledState);
   digitalWrite (ledPin4,  ledState);
   digitalWrite (ledPin5,  ledState);
   digitalWrite (ledPin6,  ledState);
   digitalWrite (ledPin7,  ledState);
           break;
         case 3: //Turn light OFF
          digitalWrite(ledPin2,  LOW);
          digitalWrite(ledPin3,  LOW);
          digitalWrite(ledPin4,  LOW);
          digitalWrite(ledPin5,  LOW);
          digitalWrite(ledPin6,  LOW);
          digitalWrite(ledPin7,  LOW);
      }   
         break;
    }
  // save the reading. Next time through the loop, it'll be the lastButtonState:
  lastButtonState = reading;
  lastcounter = counter;
}