serial communication via NewSoftSerial library with sabertooth 2*5A motor driver

Hi Arduino folks,
I have a question regarding the NewSoftSerial library.
I have a sketch which should help me to communicate with my sabertooth Motor Driver over Serial:

#include
 int x, r, l, s, f, xa, xb, xc;
#include <NewSoftSerial.h>

//serieller transmitter
 #define SABER_TX_PIN  13
 //Serieller empfänger
 #define SABER_RX_PIN  12
 //baudrate zur übereinstimmung mit den dip einstellungen
 #define SABER_BAUDRATE  9600
NewSoftSerial SaberSerial = NewSoftSerial (SABER_RX_PIN, SABER_TX_PIN );

 void initSabertooth (void)  {
   //kommunikation mit sabertooth
 pinMode ( SABER_TX_PIN, OUTPUT );
 SaberSerial.begin( SABER_BAUDRATE );
 }

 void setup()                   
 {
   initSabertooth();
   
     Serial.begin(9600);  
 }

 void set_motor()   {
   x = analogRead(0);       

 //x winkel ist  270-400 astabil bei 330
        
 
 xa = x;
 delay (20);
 x = analogRead(0);     
 xb = x;
 delay (20);
 x = analogRead(0);      
 xc = x;
 x= (xa +xb + xc)/3;

          
 //SABER_right_FULL_FORWARD 127
 //SABER_right_FULL_REVERSE 1
 //SABER_left_FULL_FORWARD 255
 //SABER_left_FULL_REVERSE 128


 s = 1.8  ;

 f = 5;


 //stabilitätspunkt bei 330
 if ((x > 325) && (x < 335)) {
 r = 62;
 l = 194;
 }
 //leicht nach vorne 310 > x < 330
 if ((x > 310) && (x < 326)) {
 r = 45;
 l = 167;
 }
 //schneller nach vorne 279 > x < 311
 if ((x > 279) && (x < 311)) {
 r = s * x - 278 + f;
 l = s * x - 148 + f;
 }
 //stark nach vorne x < 280
 if ((x > 250) && (x < 280)) {
 r = 6;
 l = 133;
 }
 // laicht nach hinten 334 > x > 349
 if ((x > 334) && (x < 349)) {
 r = 78;
 l = 208;
 }
 //schneller nach hinten fallen 348 < x < 390
 if ((x > 348) && (x < 391)) {
 
 r = s * x - 270 + f;
 l = s * x - 140 + f;
 }
 //stark nach hinten 390 < x
 if ((x > 390) && (x < 410)) {
 r = 122;
 l = 250;
 }

 //zum sabertooth senden
 SaberSerial.write(byte(r));
 SaberSerial.write(byte(l));

 }

 void loop ()  {
  
 float level = 0;

 int u;

   set_motor();
  
 }

when trying to compile this I get the following error message:
NewSoftSerial does not Name a type
I think the error occurs because of this Statement, which I’m not able to fix:
NewSoftSerial SaberSerial = NewSoftSerial (SABER_RX_PIN, SABER_TX_PIN );
Maybee it’s a thumb question but I really don’t get if I have to insert a type Definition an if so which…
Thanks in advance,
NearCZ

p.s Sorry for bad spelling(auto-correction)
and please excuse me for doing things wrong as this is my first post in the Forum… :~