Issue with Serial PINs (RX/TX) on Arduino I have an issue with an Arduino Nano.

I want to communicate with it through the Serial-Port. Meaning I want to send and receive Serial commands. With USB and the "Serial Monitor" this works nice.
Now I have connected the COM-Port of the PC with Adruinos Digital Pins 0 and 1 (RX and TX) and a GND PIN. (3 Cables total).

Here is a minimal example of my Code:

void setup() {
  Serial.begin(9600,SERIAL_8N1);
  Serial.println("Start");
}


void loop() {
  Serial.println("Hello World");

  delay( 1000 );
}


The Serial Monitor says:

Start
Hello World
Hello World
Hello World
Hello World
...


Putty however says:

▒▒▒R▒▒▒t▒*▒▒▒R▒▒▒t▒*▒▒▒R▒▒▒t▒*▒▒▒R▒▒▒t▒*▒▒▒R▒▒▒t▒*▒::
                                                     ▒▒t▒*▒▒▒R▒▒▒t▒*▒▒▒R▒▒▒t▒*▒▒▒R▒▒▒t▒*▒▒▒R▒▒▒t▒*▒▒▒R▒▒▒t▒*▒▒▒R▒▒▒t▒*▒▒▒R▒▒▒t▒*▒▒    ▒R▒▒▒t▒*▒▒▒R▒▒▒t▒*


Putty is connected with 
- BaudRate: 9600
- Data Bits: 
- Stop Bits: 1
- Parity: None
- Flow Control: None

What is wrong here?

Update:
The PC has a 9-pin D socket (Image)
This is connected to a RS232 to RJ45 connector (image)
From the RJ45-Cable I used the Brown, Blue, and White/Green Cable to connect with the Arduino
RS232 is not TTL. You need a level converter. For more details see https://www.sparkfun.com/tutorials/215.