Transfering files from Seedbox to NAS

I've read a bunch of posts about how to transfer files from a Seedbox to a NAS, but I can't seem to figure it out.I got an ultra.cc seedbox and a QNAP NAS. I was wondering if I could just transfer the files via WinSCP or other transfer clients. I tried Resilio Sync, but I came across a problem, that whenever I delete a file on my seedbox, it also deletes it on my NAS, but I want to keep the files on my NAS. Any suggestions what I can do? (Pls nothing with command lines, I get confused really quick, only something with a UI)