First, none of this is Blynk specific… rather basic Arduino learning… You can’t use the same Serial port for multiple connections!
You didn’t mention the hardware you are using… so guessing it might be your UNO.
Your Software Serial designation
DebugSerial points to the main UART (Hardware) Serial port… Don’t do that with SoftSerial, use different (supported) pins for Software Serial (and you will also need a TTL-USB adapter and a separate terminal program… I use Termite.).
And both your Blynk.begin and
Serial.print() also try to use the same default UART Serial port (AKA pins 0 & 1)… Only one or the other, you can’t use both on the same port. Typically you use the default port for programming and IDE Serial Monitor output, and a software serial port for the BT adapter &