SSDs slow down as they get full.. the more you put stuff in the SSD, the slower it gets..
this is why you should always leave some empty space inside the SSD - the more the better..
in my setting, i have one SSD to hold Windows and few online multiplayer games that i need fast loading.. however, i have 2 magnetic regular hard-drives HDD to store my files: documents, music, videos and pictures; and to store my other games that are often not online multiplayer games..
more than half of my SSD is empty..
to read more about this known problem, checkout this link
https://pureinfotech.com/why-solid-state-drive-ssd-performance-slows-down/
if your SSD is not mostly full, then it could be the HDD that is causing the delay..
if you are copying some files from your SSD into magnetic hard drive HDD (or from an HDD to your SSD), it is possible that the magnetic HDD is broken/faulty or the HDD of an older model that cannot support speeds more than 2mb/s.. i have an old USB HDD that is broken and unable to copy files as fast as before..
if the HDD is slow, then the SSD would be slow as well..