Thermal Printer doesn't print everything

Hi I have bought a GOOJPRT QR203 here thermal printer. I tried to operate it via Adafruit-Thermal-Printer-Library but unfortunately it printed nothing except for some weird characters at first. Then I played with the sketch and finally I could get it to write some meaningfull words. My problem is that the printer doesn’t print more than five characters in a single row and there are only a few words it prints accurately( like Small, Line and Taller). I am attaching the result pages . You will see there are three columns on the page, it is because I rolled the paper back to reuse it. Many thanks in advance .I simplified the sketch and it is as following;

#include "Adafruit_Thermal.h"
#include "SoftwareSerial.h"
#define TX_PIN 6 // Arduino transmit  YELLOW WIRE  labeled RX on printer
#define RX_PIN 5 // Arduino receive   GREEN WIRE   labeled TX on printer

SoftwareSerial mySerial(RX_PIN, TX_PIN); // Declare SoftwareSerial obj first
Adafruit_Thermal printer(&mySerial,4);     // Pass addr to printer constructor

const int I_NUMLOOPS = 3;
int i_loopcounter;
void setup() {

  pinMode(7, OUTPUT); digitalWrite(7, LOW);

  mySerial.begin(9600);  // Initialize SoftwareSerial
  Serial.begin(9600);  // Initialize SoftwareSerial
   printer.begin();        // Init printer (same regardless of serial type)




 
}
void printonce()
{
 
  printer.setSize('M');
  printer.boldOn();
  printer.justify('L');
  printer.println(F("Small\nTaller\nMediu"));
  printer.boldOff();
 print
}
void loop() {
  while (i_loopcounter < I_NUMLOOPS)
  {
    delay(500);
    printonce();

    i_loopcounter++;
    if (i_loopcounter == I_NUMLOOPS)
    {
      printer.feed(2);
    }
  }
}

I am attaching the result pages .

When?

void printonce()
{

  printer.setSize('M');
  printer.boldOn();
  printer.justify('L');
  printer.println(F("Small\nTaller\nMediu"));
  printer.boldOff();
 print
}

Some proof that that even compiles would be useful.

A link to the library that you are using would be useful, too.

Adafruit wrote that library to support their thermal printer. You cannot use that library for any printer you find on the cheapest Chinese market anywhere.

In opposition to your “vendor” Adafruit is supporting it’s products and provides documentation for it. Sure it costs a few bucks more but you can use it but with your printer you have to reverse engineer the supported control commands first.