Mac failure upon Sierra Update

Ok so As suggested by the title i'm in a panic because for the past week i've been trying to revive my mac following the High Sierra update.

Before the update my late 2009 imac was working fine. Last year was tested for something and the hard drive didnt show signs of any trouble.

Upon update the mac prompted a reboot when I rebooted the mac was very slow to respond and I got a white screen.

I sought help online such as PRAM SMC Recovery mode safe start up etc but to no avail

I unplugged externals etc.

when i try issue commands upon start up the mac doesnt respond immediately.

As I have said prior to the High Sierra update I had no trouble with lagging etc

when I try boot into recovery I cannot seem to see disk utility screen but a disk that says recovery and when i click on that the apple loading screen starts and i cannot get past that and after a few hours I switch off because the mac gets a bit too warm for comfort.

I tried plugging in my time machine back up and the external drive isnt showing up. I also have a bootable drive with El Capitan but that isnt showing up either

At this point I dont even care about my pictures etc because they are all saved anyway.

I tried checking the single user mode for issues but it tells me everything is fine so I really dont know what else to try.

If anyone can help me restore the mac back to health and maybe back to el capitan I would be very grateful.

Thank you in advance