How to set up synchronization from FTP to NAS according to a given schedule?

Question

NAS

Hello gentlemen, I need your bright minds and hope for assistance.
Available: NAS D-Link DNS-320L, as well as a couple of FTP resources (about 600 GB in small files)
.
Regular means through the Web interface is not possible to implement this task. I understand that some config needs to be added to cron, but here, alas, I ran into many questions. Yes, and with the world of Linux, I am exclusively on "you".
There were attempts to solve it using the Aria2 addon, although somewhere in the depths of my soul I understand that this can be implemented with standard lftp (or whoever lives there)
I swear by the boyars for your favor.

Answer 1

Read about rsync
It just resumes files, leaves rights on files, even the owner