An unsoluble problem with my monitor (flickering and random turn off)

Hi dear friends,

I have an interesting problem. I'm using LG ultragear 24gn65r-b monitor. Plugged with a type-c (thunderbolt) to display port cable to my laptop (Lenovo legion 5).

From the first day, my monitor starts flickering when I start a game. After turning on/off the monitor, flickering goes away.

On the other hand my monitor closes when I sit on my chair. I changed my chair and this issue goes away. But when I turn on (or off sometimes) my table light, my screen closes. Somehow it restarts, I'm getting a "no display" message. After a turn on/off problem goes away again.

Here's the steps that I've taken:

1) changed the cable

2) changed the switch

3) no problem with hdmi cable (but I cannot use 144 hz and freesync)

4) Reset monitor

5) Turn off energy saving mode

I don't have any other monitor so I don't want to send it to repair.

Kind regards