is there a way to download directly to a NAS

As the title suggest, I would like to be able to use TOS5 (on my Terramaster T12-423) and download directly to my NAS. Presently, I am using Filezilla on my PC and downloading to a mapped drive - but this is only giving half the download speeds I would be getting if downloading directly to my pc. I have tried using an FTP client from the Terramaster TOS store, but I couldn't connect to my seedbox account with it.
I also saw an FAQ on here regarding auto FTP to NAS, but I couldn't understand the reply. This is my first NAS unit, I am somewhat competent, but I obviously need a lot more education.
thanks for your help.