serial.read output weird symbols

i’m a Arduino newbie working on a school project

I’m working with Arduino Uno and a HC-05 Bluetooth module. Trying to test out the Bluetooth communication both receiving and sending. The set up seems to be right, but when confirming the data received from Serial.read() with a serial monitor (I use putty), it is showing some weird symbol. Please help me.

void setup() {
  // initialize serial communication at 9600 bits per second:
  Serial.begin(9600);
  Serial.println("Hello.");
  Serial.println();
  delay(5000);  //delay 5 secs
}

// the loop routine runs over and over again forever:
void loop() {
  // read the inputs on analog pin 0 and pin 1:
  int sensorValue1 = analogRead(A0);
  int sensorValue2 = analogRead(A1);

  // Convert the analog reading (which goes from 0 - 1023) to a voltage (0 - 5V):
  float voltage1 = sensorValue1 * (5.0 / 1023.0);
  float voltage2 = sensorValue2 * (5.0 / 1023.0);
  
  // print out the value from analog pin 0:
  Serial.print("Sensor Voltage 1 = "); Serial.println(voltage1);
  Serial.println();
  delay(500);    
  
  if( Serial.available() )  // if data is available to read
  {
    // variable to receive data from the serial port
    char key;
    key = Serial.read();   
    delay(10);
    // print out the character received from the serial port
    Serial.print("Command Received: ");
    Serial.println(key);
    // print out the converted voltage value from analog pin 1
    Serial.print("Sensor Voltage 2 = "); Serial.println(voltage2);
    Serial.println();
        
    if( key == 'o' )           // if 'o' was received, print message
    {
       Serial.println("Hello again");
       Serial.println();
    } 
  }  
}

Is the Serial port talking to the PC or is it talking to the Bluetooth device? Yes is wrong answer. So is both.

both PC and Blutooth. The output confirms that. But when I type a character (any character) on keyboard, it is showing up as random symbols. I don't know why.

both PC and Blutooth.

Didn't I say both was the wrong answer? Is your bluetooth device really communicating at 9600 baud? Most do not. Most communicate at 115200.

if I'm receiving data from Bluetooth to PC at 9600, it doesn't work the other way (PC to Bluetooth)?

i tested with different baud rate by changing Serial.begin() and putty setting. It only works with 9600. am i missing something else?

Can you show your wiring? How are you communicating with the PC and the Bluetooth module at the same time?