Im new in this so i would like some help with MKR 1000

Projects Programming
1

I was doing some project from youtube and I did just like him. But I got a lot of errors that I don't understand and I spend an hour and a half on looking for answers. I'm totally new in this so I still don't understand everything. I would really appreciate your help.
Here is code:

const int ledPin = 13;

void setup() {
Serial.begin(9600);
pinMode(ledPin, OUTPUT);

}

void loop() {
int delayPeriod = 100;
int countDir = 1;
digitalWrite(ledPin, HIGH);
delay(delayPeriod);
digitalWrite(ledPin, LOW);
delay(delayPeriod);

countDir = checkDirChange(delayPeriod, countDir);

delayPeriod += 100 * countDir;
Serial.print("new wait time:")
Serial.println(delayPeriod)
}

int checkDirChange(int delayPeriod, int countDir){
if((delayPeriod == 1000) || (delayPeriod == 0)){
countDir *= -1;

if(countDir <0){
Serial.println("going down");

} else {
Serial.println("going up");
}
}
return countDir;
}

AND HERE ARE ERRORS:

In file included from C:\Users\adria\OneDrive\Dokumenti\ArduinoData\packages\arduino\hardware\samd\1.6.21\cores\arduino/delay.h:23:0,

from C:\Users\adria\OneDrive\Dokumenti\ArduinoData\packages\arduino\hardware\samd\1.6.21\cores\arduino/Arduino.h:81,

from sketch\Tut_1.ino.cpp:1:

C:\Users\adria\OneDrive\Dokumenti\Arduino\Tut_1\Tut_1.ino: In function 'void loop()':

C:\Users\adria\OneDrive\Dokumenti\ArduinoData\packages\arduino\hardware\samd\1.6.21\variants\mkr1000/variant.h:200:37: error: expected ';' before 'SerialUSB'

#define Serial SerialUSB

^

C:\Users\adria\OneDrive\Dokumenti\Arduino\Tut_1\Tut_1.ino:22:3: note: in expansion of macro 'Serial'

Serial.println(delayPeriod)

^

exit status 1
Error compiling for board Arduino/Genuino MKR1000.

Link of video: Arduino Programming - YouTube

Thank you ahead
ERROR_420

2 
 Serial.println(delayPeriod)
 }

The errors are bit misleading. It is this statement that is missing a semicolon.

3

And the one before it.