internal harddisk removal

Hi there all,

I've got an iMac late 2012, 3,4 GHz Intel Core i7, 32 GB 1600 MHz DDR3, NVIDIA GeForce GTX 680MX 2048 MB on system 10.11.6 running.

The internal harddisk of 3tb is suddenly after over 4 years removing it self, and then i got the message that i didn't correctly removed the harddisk (without removing it my self).

That happend several times, but it happend more frequently and rapidly.

Now it doesn't show up at all anymore, not even in the best repair applications.

Is my harddisk dead, or is there more to it.

And then the most frustrating part, on my older iMac late 2009, i could easily remove the front of the monitor.

So i thought i remove the front an i replace the harddisk with a new one, and then it happend, i busted the glass of my iMac @!#@#$@?><#@. GRRRRR. I don't understand why apple had to change the way the screen can be removed. Now i also have to buy a new glass.

But anyway, is there somebody who can help me out whats wrong with my harddisk?

Thanks,

Dave