2nd Monitor HDMI works for 5 secs and then start flickering / noisy display in Open core Cataline

hi guys! I installed Catalina thru OC I have Dell Inspiron 5559 with i3-6100U Skylake with 520 HD intel GPu

Accelration is working fine

but when I connect my monitor HDMI to VGA the display show in the preferences I am using a LG okay then I can see the macOS on the 2nd screen for about 5 to 8 secs and after that it is vanished! and colourful light flicker ! what to do

Like this on 2nd screen but my Laptop internal screen is working perfectly then one I am using to type