Problem using Serial Monitor on MKRZERO

[probierer]

So I have an MKRZERO and I tried the simple blink sketch, which works fine. But than I tried to log some data over Serial. I used this Sketch: 

Code: [Select]

void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(LED_BUILTIN, OUTPUT);
  Serial.begin(9600);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);                       // wait for a second
  Serial.println("Hallo");
}
 In Theory it should print "Hallo" every 2 seconds. After it uploads it changes its port like all mkr ports, but when I tr to open this port it says: (Port busy). But there is no other service using this Board.. I checked with Windows process Explorer. (The Blink Sketch still works)!

I already:
    restareted my computer
    deleted all hidden Ports and reinstalled them
    change Pc ports

Also I think it has something to do with my PC setup because it worked on a friends Laptop! I use Windows 10 with Arduino 1.8.13

Also after Uploading I have to double click the reset button to upload again. Is this normal? Shouldnt it switch automatically to bootloader? 

Thanks for the Help!