Extremely slow file transfer speeds from usb 3.0 to external hdd

I just bought an external hdd (Seagate Expansion 2tb 4.8gbps) why are my files being transfered at under 100mbps? The advertised transfer rate for my external hdd is 4.8gbps but it starts only at 100mbps then drops regardless of file type and size.

Well… what do you expect for i think 59$? Naturally they are only caching with slower memory behind that. Likely a slow 5400rpm drive. Nevermind the high rma rate of the sold devices.
Also this is not really the correct forum for this. You might be better off venting in the review section of the shop where you bought it.

I paid for it in brazilian reals (R$500) also everyone reported that it is fast but to me the speeds are pretty poor, i dunno what’s causing this, does the speed vary depending on file type and size? It seems to me that images for example are faster to transfer and larger files like bin an isos are slower.