Cloudy dust like , spreading slowly inside my Pc Monitor

That’s usually due to layer delamination due to a panel defect, especially if it spreads over time. The problem is you can’t fix this without replacing the entire panel. Unless the panel is fine and it just needs to be cleaned out internally (which is still a risk, but it’s doable if you’re careful), it’s usually unrepairable.

The problem is with most 1st party panel manufacturers, it’s typically cheaper to replace the monitor as a unit due to the cost of the actual panel itself, and this is usually the case with LG and Samsung as they make their own panels. That being said, sometimes Samsung doesn’t use their own and uses a 3rd party one, so they also are sometimes cheap to salvage - it’s usually AUO if this happens. However, unless you can find a cheap panel, it’s usually better to replace the monitor as a unit since it’s almost always a lose-lose proposition cost wise. Acer, AOC and Dell are not panel manufacturers, so you can somethimes get off lucky with those types of monitor brands.

Make sure you reset the panel hours as well if you find one that’s brand new. On Samsung, set the brightness and contrast to 0, exit the adjustment mode (if needed - not always required) and hold down input. For joystick control, navigate to input and hold it down until the service menu comes up. Hold menu on panel hours for 3 seconds and it resets.

You’re one of the unlucky ones :-(. This uses a Samsung LTM panel (LTM185AT01). Since this doesn’t look like one where AUO panels are a backup plan for short internal supply, the panel likely won’t be cheap when you can get something newer with a more current port configuration (or at least a DVI/VGA with a DHI->HDMI adapter included in the box - which Samsung sometimes does with their older designs to cover for the fact many new GPUs and towers no longer use DVI). The service manual can be found here (translation required). It’s also not readily available new, so you may need to get a used one on eBay with minor issues at a discount you can accept, or at least find the AUO equivalent part if multiple panels were used and try your luck.