Error when loading a code

This is my code and whenever I upload this particular one it gives me an error as shown below. And once this error shows up for this particular code it doesnt allow me to upload any other code either such as the simple blink LED code. Please help!!

ARDUINO CODE:

#include <Stepper.h>
String readString, Stepper1, Stepper2;
Stepper stepper1(20000, 2,3);
Stepper stepper2(6000,8,9 );

void setup() {
 Serial.begin(9600);
 stepper1.setSpeed(100);
 stepper2.setSpeed(100);
 Serial.println("servo-test-21"); // so I can keep track of what is loaded
}

void loop() {

 while (Serial.available()) {
   delay(10);  
   if (Serial.available() >0) {
     char c = Serial.read();  //gets one byte from serial buffer
     readString += c; //makes the string readString
   } 
 }

 if (readString.length() >0) {
     Serial.println(readString); //see what was received
     
     // expect a string like 07002100 containing the two servo positions      
     Stepper1 = readString.substring(0, 5); //values corresponding to the number of steps available for one revolution
    // int Stepper1 = conversion1 - '0';
     Stepper2 = readString.substring(6, 9); //
     //int Stepper1 = conversion2 - '0';
     
     Serial.println(Stepper1);  //print to serial monitor to see results
     Serial.println(Stepper2);
     
     int n1; //declare as number  
     int n2;
     
     char carray1[6]; //magic needed to convert string to a number 
     Stepper1.toCharArray(carray1, sizeof(carray1));
     n1 = atoi(carray1); 
     
     char carray2[6];
     Stepper2.toCharArray(carray2, sizeof(carray2));
     n2 = atoi(carray2); 

     int Steps1=n1/(0.018*2);   //divide by number of degrees per step in order to get total no. of steps
     int Steps2=n2/(0.056*2);   // divide or times by two? CHECK!!!

     
    if(Steps1>0,Steps2>0){      //this is so it can move in two different directions
     stepper1.step(Steps1);
    
    stepper2.step(Steps2);
    }
    else if(Steps1<0,Steps2<0){
    stepper1.step(-Steps1);
    
    stepper2.step(-Steps2);
    }
    }
    
   readString="";
 }

ERROR THAT SHOWS UP:

Sketch uses 1,120 bytes (3%) of program storage space. Maximum is 32,256 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2,039 bytes for local variables. Maximum is 2,048 bytes.
An error occurred while uploading the sketch

The sketch compiles, but you have a connection problem. Troubleshooting might help.

If you are new at programming you might want to turn up the warning levels in Preferences. When I do that with your code it points out a mistake:

/Users/john/Documents/Arduino/sketch_aug02d/sketch_aug02d.ino: In function 'void loop()':
/Users/john/Documents/Arduino/sketch_aug02d/sketch_aug02d.ino:53:16: warning: left operand of comma operator has no effect [-Wunused-value]
     if (Steps1 > 0, Steps2 > 0) { //this is so it can move in two different directions
                ^
/Users/john/Documents/Arduino/sketch_aug02d/sketch_aug02d.ino:58:21: warning: left operand of comma operator has no effect [-Wunused-value]
     else if (Steps1 < 0, Steps2 < 0) {
                     ^

Putting a comma between the expressions does not test both. Put ‘&&’ if you want the ‘if’ to execute only if BOTH are true or put ‘||’ if you want the ‘if’ to run if EITHER is true.

thank you!!