You can use
Auslogics Disk Defrag to defrag rather than windows defragger. Koala showed me that a long time ago and its much faster than regular defrag and you don't need 15% free space.
And make sure your computer is clean and dust free, I think if the HDD gets hot which I think is rare but if it does get hot, pins won't be Aline as much anymore so it won't run as well.