无法分离实现和接口

我无法编译以下文件。我试图将姓名和年龄传递给一个对象，在检查并将每个年龄分配给适当的类别(成人、儿童…)后，我试图打印它。

我的3个文件如下：

第一个1:

//cannot access private member declared in class Person
//No constructor could take the source type, or constructor overload resolution was ambiguous.
#include <iostream>
#include <string>
using namespace std;
#include "person2.h"
void getData(Person&);
void displayData(Person&);
int main(){
Person p;
getData(p);
displayData(p);
}
void getData(Person& p){
cout<< "Enter the name: ";
cin>> p.name;
cout<<"Enter the age: ";
int age;
cin>> age;
p.setAge(age);
p.ageGroup = p.determineAgeGroup(age);
}
void displayData(Person& p){
cout<<p.name<< " is in the group of " << p.ageGroup <<endl;
}

第二个：

#include <iostream>
#include <string>
using namespace std;
class Person {
public:
string name;
string ageGroup;
void setAge(int&);
string getAge();
string getAgeGroup(int);
private:
int age;
string determineAgeGroup(int );

}；

第三个：

#include <iostream>
#include <string>
#include "person2.h"
using namespace std;
void Person::setAge(int& a){
if(a<0) cout<< "No";
}
string Person::getAge(){
return age;
}
string Person::determineAgeGroup(int a){
if(a>= 65) return "Senior";
else if(a<65 & a>= 20) return "Adult";
else if(a<20 & a>= 13) return "Teen";
else return "Kid";  
}
string Person::getAgeGroup(int a){
return determineAgeGroup(a);<<endl;
}