How to get a human readable process name (like in the task manager) via Win32 API?

Question

I try to detect the process name of a currently active window. I have the following code.

#include <iostream>
#include <functional>
#include <thread>
#include <windows.h>
#include <Psapi.h>

using namespace std;

int main()
{
    while (true) {
        wchar_t buffer[512];
        HWND hwnd = GetForegroundWindow(); // get handle of currently active window
        DWORD processId;
        GetWindowThreadProcessId(hwnd, &processId);
        auto processHandle = OpenProcess(PROCESS_VM_READ | PROCESS_QUERY_INFORMATION, false, processId);

        DWORD length = sizeof(buffer) / sizeof(buffer[0]);
        auto success = QueryFullProcessImageNameW(processHandle, 0, buffer, &length);

        if (success) {
            wcout << endl << buffer << endl;
        }
        else {
            wcout << endl << L"An error has occurred. Code: " << GetLastError() << endl;
        }

        std::this_thread::sleep_for(std::chrono::milliseconds(1000));
    }
}

It works well, but currently the path to the executable is printed into the console, e.g.

C:\Program Files (x86)\Opera\68.0.3618.63\opera.exe

But I would like to get a human readable name of the process, as in the Windows Task Manager, that is:

Opera Internet Browser

Also, when I select the Task Manager's window, the current code just prints an error code:

An error has occurred. Code: 6

Thus, how to get a process name like in the Task Manager via WinAPI?