Why doesn't a few simple changes work?

As I understand the arduino forum it is not for serving fish (ready to use code) it is for teaching fishing. Learning how to code yourself with the support of the forum-members.

The greater specificness is to self-writing a few lines of C++-code
wperko he himself writes a few lines of code as his own attempt and then asks for what to change to make it work.

As a first hint:
receive characters on the serial port of your arduino uno.
The serial input basics tutorial example 4

// Example 4 - Receive a number as text and convert it to an int

const byte numChars = 32;
char receivedChars[numChars];   // an array to store the received data

boolean newData = false;

int dataNumber = 0;             // new for this version

void setup() {
   Serial.begin(9600);
   Serial.println("<Arduino is ready>");
}

void loop() {
   recvWithEndMarker();
   showNewNumber();
}

void recvWithEndMarker() {
   static byte ndx = 0;
   char endMarker = '\n';
   char rc;
   
   if (Serial.available() > 0) {
       rc = Serial.read();

       if (rc != endMarker) {
           receivedChars[ndx] = rc;
           ndx++;
           if (ndx >= numChars) {
               ndx = numChars - 1;
           }
       }
       else {
           receivedChars[ndx] = '\0'; // terminate the string
           ndx = 0;
           newData = true;
       }
   }
}

void showNewNumber() {
   if (newData == true) {
       dataNumber = 0;             // new for this version
       dataNumber = atoi(receivedChars);   // new for this version
       Serial.print("This just in ... ");
       Serial.println(receivedChars);
       Serial.print("Data as Number ... ");    // new for this version
       Serial.println(dataNumber);     // new for this version
       newData = false;
   }
}

As another hint:
once the serial data including the end-marker is received the evaluation of the received characters can start.
As the datasheet shows each phonem is represented by a number
There must be done a translation from phonem to the corresponding number.
that is then transferred to the trovax-chip with the say-function
best regards Stefan