How to read a specific amount of data via serial? I'm trying to send data via serial from my Arduino nano to my ESP. Its an integer from 1 to 4 digits
so something like 0, 13, 1234, 123, ...

Every thing works fine but when the data comes too fast it stopps the output and  then it print all the data on the screen.

I use this method to recieve data.

void loop() { // run over and over
        if (Serial.available()) {
                incomingByte = Serial.readString();
                Serial.println(incomingByte);
        }
}
From what you have posted, assuming this is the ESP code in the question, it is clear that for every character the Arduino sends the ESP the ESP will send 3 back. So at some speed this will likly stop working