Serial Monitor shows values just after unplugging and replugging the USB

Hello dear Arduino Community,

I hope this topic is in the right Forum part.

My problem:

Recently I bought an ESP32 and tested it with the Blink - Test provided in the Examples. When I want to output some value in the Serial monitor, the Serial Monitor stays blank.
I discovered that when I disconnect and reconnect the USB - cable from the ESP to the Laptop the Serial Monitor shows what it is supposed to show.
To simplify the test, I just tried a "Hello World" example, but the same problem occurs.

Long way short, the Serial Monitor just outputs anything after the device is disconnected and reconnected.

Here I will show you the first code I used, and afterwards the "Hello - World " sketch.
Maybe someone has any idea how to solve that.
I would be really grateful.

int vibr_Pin = 4; 
int LED_Pin = 2;

void setup(){
 
  Serial.begin(115200); //init serial 9600
  pinMode(LED_Pin, OUTPUT);
  pinMode(vibr_Pin, INPUT); //set vibr_Pin input for measurment
 // Serial.println("----------------------Vibration demo------------------------");
}
void loop(){
  long measurement =TP_init();
  delay(50);
 // Serial.print("measurment = ");
  Serial.println(measurement);
  if (measurement > 1000){
    digitalWrite(LED_Pin, HIGH);
  }
  else{
    digitalWrite(LED_Pin, LOW); 
  }
}

long TP_init(){
  delay(10);
  long measurement=pulseIn (vibr_Pin, HIGH);  //wait for the pin to get HIGH and returns measurement
  return measurement;
}

The "Hello - World sketch":

void setup() {
  // put your setup code here, to run once:
Serial.begin(115200);
}

void loop() {
  // put your main code here, to run repeatedly:
Serial.print("Hello World");
delay(5000);
}

Serial.begin(115200); //init serial 9600

Is your serial monitor speed set to 9600 or 115200?

What kind of ESP32 module do you use? Can you show a picture of it?