Backup system

[Judith08]

Hi,

I wonder what the best way is to back up my photos. 

How it is now:
I have 1 PC with C + D drive, both sync to my NAS (Synology rate 5, DS411+II). The C drive is in rate and I thought the D too, but that has changed apparently..., the D drive crashed this week and I found out that the software didn't sync to my NAS, so I lost all my work photos from the last 7 years. This is awful because I thought I had it all in order. If you know of somebody who can help retrieve data too?

Since 1 year I have a shop where I work from my macbook Pro. I now have photos there in LR too. 

Now I want a second NAS at a different location in case my first NAS gets stolen.

Is there a better way than just a NAS as  second backup? (in the cloud is too slow for here).
And what is the best way to sync/backup files? I now have it that when I delete files at point A, it deletes it everywhere, my husband says that is the wrong way, that this is not a save backup.

Also, I'm finally into the RAW class, but don't have time now to do this whole course before I can sort out how to work/archive without LR. I don't know raw and wonder what to do now, because I just don't know what to do anymore. Thank you.