How to create multiple serial.read character??

Using Arduino Project Guidance
2

You should find a better translator. Try google translate. Many of us are not native English speakers so your poor English is really not helping us understand what you want.

I guessed what you want is to capture X and then A from serial port and do something when this happens.

You have a loop, the loop() function to loop around while you check for X. That works. You need another loop to check for A:

void loop()
{
char in_byte=0;

while (!serial.available()) //Wait for incoming character
{}

in_byte=Serial.read();
if (in_byte=='X')
{
  while (!serial.available()) //Wait for incoming character
  {}
  in_byte=Serial.read();
  if (in_byte=='A')
  {//Do your X then A action
  }
}
}