#include <iostream>
#include <fstream>
#include <string>

using namespace std;

int main()
{
  string contain_of_file,bufor,word,empty=" ",new_line="n";
  string conection;
  string::size_type position;
   cout<<"Give a word";
 cin>>word;
 ifstream NewFile;
 ofstream Nowy1;
 Nowy1.open("tekstpa.txt", ios::app);
 NewFile.open("plik1.txt");
 while(NewFile.good())
{
     getline(NewFile, contain_of_file);
    cout<<contain_of_file;

   position=contain_of_file.find("Zuzia");
    if(position!=string::npos)
    {
    conection=contain_of_file+empty+word+new_line;
  Nowy1<<conection;
    }
   Nowy1<<contain_of_file;

}
Nowy1.close();
NewFile.close();

cin.get();
return 0;
}

while (std::getline(NewFile, contain_of_file)) { ... }

Nowy1 << contain_of_file << ' ' << word << 'n';