I’m just trying to learn to program a few things, and a game loop is one of those.

This game loop only process Windows messages, but it can not even handle 30 fps.
This is true also if the message processing is done only once per loop, replacing WHILE with IF.
I use QueryPerformanceCounter() function to get number of 100ns ticks before work is done and after, subtracting them to get time used. Loop time is 100ns * 166666 * 2 = 0.0333332s.
The boolean ‘timeExceeded’ is set if the the wait time is positive, indicating that time used is more than the intended loop time.
What to do?

    // timer data
    LARGE_INTEGER start_time;
    LARGE_INTEGER end_time;
    LARGE_INTEGER rest_time;
    LARGE_INTEGER loop_time;
    loop_time.QuadPart = -166666LL*2;   // loop time

    bool timeExceeded = false;      // does time exceeds loop time


    // message loop data
    MSG msg = { };
    bool running = true;

    while (running)
    {
        // measure time
        if (!QueryPerformanceCounter(&start_time))
            break;

        // process messages
        while (PeekMessage(&msg, 0, 0, 0, PM_REMOVE))
        {
            if (msg.message == WM_QUIT)
                running = false;
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }

        // other work

        // Get elapsed time and wait for (30hz - elapsed time)
        if (!QueryPerformanceCounter(&end_time))
            break;

        rest_time.QuadPart = loop_time.QuadPart + (end_time.QuadPart - start_time.QuadPart);
        if (rest_time.QuadPart >= 0)
        {
            timeExceeded = true;
            continue;
        }
        if (!SetWaitableTimer(hTimer, &rest_time, 0, 0, 0, 0))
            break;

        if (WaitForSingleObject(hTimer, INFINITE) != WAIT_OBJECT_0)
            break;
    }

    // clean up
    CloseHandle(hTimer);
    
    return 0;
}