The S.M.A.R.T. stats monitored by HDDs were chosen because HDD manufacturers noticed they were highly correlated with drive failures. While getting one of these warnings does not guarantee your drive will fail soon, it is highly likely.
ImperialCavalry :
it is possible this is a false alert? Never got a something like this before, Uncorrectable Sector Count is zero so does the
Reallocated Sectors Count, (real value) My computer also sees the hard disk just like before
That's one of the few S.M.A.R.T. warnings which indicates a guaranteed failure.
As the years go by, it's unavoidable that some sectors of the HDD will go bad (can't reliably read data written to that sector anymore). Because of how common this is, HDDs are manufactured with a few tens or hundreds of thousands of reserve sectors. When a sector fails, a note is made in the drive's firmware not to use that sector again. Instead, one of these reserve sectors is mapped ("reallocated") to the failed sector, and it is silently substituted every time the filesystem requests data from the known-bad sector.
Your warning indicates the HDD has used up all its reserve sectors. Any subsequent failed sectors will go uncorrected and will result in data loss. Get a new drive and copy your data to it ASAP. You probably have already lost some data (won't be able to copy it off your old drive because it can't read it properly off the bad sectors). And continuing to use the drive just gives other sectors more time to go bad, making it harder to copy 100% of your data to the new drive.
If this were an old drive (like 15+ years old), the problem would not be so urgent as you probably exhausted the reserve sectors naturally. But since the drive is only 3 years old, it's likely a bearing or spindle is failing or has come loose, and the inside of the drive is wobbling slightly making it difficult for the heads to reliably read data, leading to a higher than normal sector failure rate and your drive using up its reserve sectors too quickly. The longer you put off getting a new drive, the greater the risk of a catastrophic failure (bearing or spindle fails completely) and you losing all your data.
strange thing is disk performance is same as before its fine, I thought failing disks have reduced speed over time
There's a ton of error-correction coding (ECC) used in HDDs. It's like how you can scratch a CD or DVD and it'll still play just fine. Up to a certain point when you exceed the ECC's capability to recover the original data, and it fails entirely. Kinda like how on old analog TVs (no ECC) the image would slowly turn into snow as the signal weakened. But on newer digital TVs (where the video stream has ECC) you either get a clean image or no image, with a very small transition in between.