array bound is not an integer constant before ‘]’ token

Question

#include <iostream>
using namespace std;

int limitUsernames = 0, limitPasswords = 0, lastUsername = 0, lastPassword = 0;
string loggedUsernames[limitUsernames], loggedPasswords[limitPasswords];
string tryUsername, tryPassword, loginUsername, loginPassword;

class Register {
public:
bool checkUsernameAvailability() {
string checkUsernames;
bool usernameTaken = false;
bool usernameAvailabilityStatus = true;
for (int iterator = 0; iterator < limitUsernames; iterator++) {
checkUsernames = loggedUsernames[iterator];
if (checkUsernames == loggedUsernames) usernameTaken = true;
}
if (usernameTaken == true) {
usernameAvailabilityStatus = false;
}
return usernameAvailabilityStatus;
}
void registerUsername() {
cout << "Enter username: ";
cin >> tryUsername;
if (checkUsernameAvailability()) {
lastUsername = limitUsernames;
limitUsernames++;
loggedUsernames[lastUsername] = tryUsername;
cout << "Username successfully registered.";
}
else {
cout << "Error at line 26 - Username already taken." << endl << "Function checkUsernameAvailability() returned false." << endl;
}

}
};

class Password {
public:
void registerPassword() {
cout << "Enter password: ";
cin >> tryPassword;
lastPassword = limitPasswords;
limitPasswords++;
loggedPasswords[lastPassword] = tryPassword;
cout << "Password registered into account.";
}
};

class AccountLogin {
public:
bool checkUsernameExistence() {
bool usernameExistenceStatus = false;
for (int iterator = 0; iterator < limitUsernames; iterator++) {
if (loginUsername == loggedUsernames[iterator]) {
usernameExistenceStatus = true;
int indexOfUsername = iterator;
}

Answer 1

I hurt my eyes 👀.
please don't just copy paste your codes here, put them well organise in a code format(code playground) and paste the link of it here.
I hope you understand.
(where's my eye-drops? 👁️‍🗨️)