WD My Passport 2017 gone slow on read and write speed, failed on WD Drive Utilities' Quick Drive test, and sudden lags upon usage

Hi, I have bought a WD My Passport 2017 last September 26, 2018. I have been using it frequently for almost 2 years, upon plugging in yesterday (July 29, 2020), the portable hard drive have gone very slow in responding to my actions (checking my files inside) and have gone very slow in copying and reading a file. I tried transferring a 4.7GB video file but the copying speed have gone way below its average copying speed before. I tried also performing diagnostic tests on the portable hard drive but the device was failing upon the WD Drive Utilities’ Quick Drive Test, but on the other hand the device was tested using “Run Drive Status Check” and positively reported a “SMART status passed”. The portable hard drive was filled with files (music and movie files) down to the limit of its capacity (almost 6GB left out of 1TB storage capacity). And also I have tried a third-party software (Glary Utilities Pro) performing a Disk Defragmentation and Check Disk on my portable hard drive and it came out good on results, no errors and bad sectors found on the drive and disk defragmentation was completed successfully without any reported problems. What can you guys advice and recommend upon this issue?

The quick drive test checks the drive for major performance problems. Whereas, the WD Drive Utilities’ complete drive test checks every sector for error conditions, and inserts bad sector markers as required.