Thanks for this guide and also to this
guide I was able to fix the no HDMI output problem.
But now my problem is when I hot unplug the HDMI from my laptop (external monitor is powered ON while unplugging), my laptop monitor turns black screen only (laptop is still functioning normally,I think...) , I tried closing the LID then open again to see if the display will go back to normal but nothing happens, so I have no choice but to turn OFF and ON again my laptop. After restart and login I connect again my laptop to the external monitor thru HDMI then I tried to cold unplug the HDMI from my laptop (external monitor is powered OFF while unplugging), the display on my laptop return as normal. Now I'm confused which part I did wrong.
I am running macOS High Sierra 10.13.6