How to expand dynamically allocated array in C++?

I have tried to implement solution to dynamical expansion of array as user is entering new data in main as shown:

ComplexNumber** nizKompl = new ComplexNumber*[1];
bool unos = true;

while(unos){
  cout << "Unesite novi kompleksni broj(realni imaginarni): ";

  if(cin >> re >> im){ 
    nizKompl[brojUnesenih] = new ComplexNumber(re,im);
    ++brojUnesenih;

    ComplexNumber** nizTemp = new ComplexNumber*[brojUnesenih+1];
    copy(nizKompl, nizKompl+brojUnesenih, nizTemp);

    for(int i=0; i<brojUnesenih; ++i){
      delete nizKompl[i];
    }

    delete [] nizKompl;
    nizKompl = nizTemp; 
  } else {
    cout << endl << endl;
    unos = false;
  }
}

ComplexNumber is custom type. ComplexNumber works fine but I am having problem with double free or corruption error as I am entering new data and creating new ComplexNumbers in program.

Is there some better way to achieve this? I need to use dynamical array because It is for educational purpose.

As I understand double free error occurs when you try to free memory which is already free'd. But It seems that I just can't resolve the issue, as I can see no double free should happen.

Is something happening in memory of which I have no knowledge? Is it problem with std::copy as I am copying array of pointers of pointers?

I would really appreciate any help or suggestion. Thank you!