Static text and scolling text in same row Display P10

. i already fix and more shorten my code so more easier. i dont know actualy how to make limit margin for left scrolling. using boudrate 9600 for send text . example : 1A| Chicago - Kansas , that mean with seperator "|" i can use for 1A (stay Display) and Chicago - Kansas is scrolling text, i already did it, but im not so satisfied because screen seem not smooth, its break when moving the text. im using DMD2.

#include <SPI.h>
#include <DMD2.h>
#include <fonts/SystemFont5x7.h>
#include <fontTje.h>
#include <EEPROM.h>
#include "Arduino.h"
char rChar;
const int WIDTH = 2;
const uint8_t *FONT = fontTje;
int panjang;
SoftDMD dmd(2, 1);
SoftDMD dmd1(2, 1);
DMD_TextBox box(dmd1, 0, 1);
DMD_TextBox box1(dmd, 20, 1);
String command;
String readString;
int i;
int counting = 1;
#define maxChar 500
char runningText[maxChar];
byte index;


void ep() {

  if (Serial.available() > 0 ) {
    for (i = 0; i < 499; i++) {
      EEPROM.write(i, 0);
    }
    for (i = 0; i < 499; i++) {
      runningText[i] = '\0';
      EEPROM.write(i, runningText[i]);
    }
    index = 0;
  }
  while (Serial.available() > 0) {
    if (index < (maxChar - 1)) {
      rChar = Serial.read();
    
      runningText[index] = rChar;

      EEPROM.write(index, runningText[index]);
      index++;
      runningText[index] = '\0';
    }
  }
  for (i = 0; i < 499; i++) {
    runningText[i] = EEPROM.read(i);
  }
}
void setup() {
  Serial.begin(9800);
  dmd.setBrightness(500);
dmd.selectFont(FONT);
  dmd.begin();
  ep();
}
void des () {
  ep();
  String varA = runningText;
  String tug = varA.substring(0, strlen);
  const char* hub = tug.c_str();
  char* cim = strtok(hub, "|");
  dmd1.selectFont(FONT);
  String sep = "|";
  String a = cim + sep;
  a.trim();
  panjang = a.length() * 8 - 1;
  (panjang);
  dmd.begin();
  dmd.drawString(0, 1, a );
}

void loop(void) {

  ep();

  des();
 
  xscr();
}
void xscr() {
  String varA = runningText;
  String tax = varA.substring(0, strlen);
  const char* mg = tax.c_str();
  String tx = strtok(mg, "|");
  String v = "|";
  String scr = tx + v;
  const char* mk = scr.c_str();
  char* sctext = strtok(NULL, "|");
  String myString = String(sctext);
  myString.trim();

  const char *next = sctext;
  while (*next) {
    Serial.print(*next);
    box1.print(*next);
    delay(100);
    next++;
  }
  box.clear();

}

Your post was MOVED to its current location as it is more suitable