string in eeprom

You havet to put a null terminator on each string AND you have to make room for that terminator when you allocate the arrays:

  char slowo1[6];
  char slowo2[8];
  char slowo3[7];

  for (int i=0; i<5; i++) {
    slowo1[i]=EEPROM.read(0+i);
  }
  slowo1[5]='\0';

  for (int i=0; i<7; i++) {
    slowo2[i]=EEPROM.read(5+i);
  }
  slowo2[7]='\0';

  for (int i=0; i<6; i++){
    slowo3[i]=EEPROM.read(12+i);
  }
  slowo3[6]='\0';

  Serial.print(slowo1);
  Serial.print(slowo2);
  Serial.print(slowo3);
  Serial.print("greta");