Calling a function from another process

I apologize in advance for my English :D

How can I call a function from a process, knowing the pointer to it?

I tried this:

Process.cpp:

DWORD pid;
HWND hwnd;
HANDLE phandle;

void Attach() {
    hwnd = FindWindow(NULL, L"GTA:SA:MP");
    if (!hwnd) {
        cout << "Process is not found" << endl;
        system("pause");
    }
    else if (hwnd) {
        cout << "Process was successfully loaded" << endl;
        GetWindowThreadProcessId(hwnd, &pid);
        phandle = OpenProcess(PROCESS_VM_READ, 0, pid);
    }
    else
    {
        cout << "Error 0x01" << endl;
        system("pause");
    }
}

void GameText(const char* szText, int iTime, signed int iStyle)
{
    typedef void(__stdcall* GameText_t)(const char*, int, signed int);
    GameText_t pGameText = (GameText_t)((char*)phandle + 0x69F2B0);
    return pGameText(szText, iTime, iStyle);
}

main.cpp:

int main()
{

    std::cout << "Hello World!\n"; 

    Attach();

    GameText("~r~Test!", 1000, 5);

}

And I get the following exception:

An exception was thrown at the address 0x006EF7B6 in wh_mta.exe: 0xC0000005: access violation during execution at 0x006EF7B6.

Why is this happening? How can I call a function by its pointer through HANDLE?

P.S

Reading an integer through HANDLE works great.

int Read_Int(int address) {
    int value;

    ReadProcessMemory(phandle, (void*)address, &value, sizeof(value), 0);

    return value;
}

Maybe 30 years ago that would have worked :D :D :D

Processes can't access each other's memory… Every process has their own image of the memory, so address 0xWHATEVER in a process does not contain the same data as 0xWHATEVER in another process!

You need to make a library or use some inter process communication (IPC).