Thsi drive is quite cheap.
There a multiple factors that a re slowing down your SSD:
The least storage a SSD has the slower it will run.
Drive's specs don't really specifiy greatly what kind of NAND flash its using (only 3D), which could result in it being QLC which is known to be the worst kind of NAND flash. This NAND slows down after lots of data transfer. Linus' video:
Not really for thsi drive but it uses the same NAND.