using a NAS RN102 both as a DDNS ftp server and a local network drive. Is that possible?

Hello everybody

I installed about 2 years ago a RN102 NAS at my home in order to have a couple of my websites (remotely hosted) send a daily backup to my NAS.

I managed to enable ftp access with DDNS, and I get my backup files every evening as expected. So it works fine.

My NAS is connected to my fritzbox router and if I remember well, I had to open some ports in the router to let the ftp work through.

The NAS has currently only 1 bay equipped (we be expanded to 2), and is running under OS 6.5.1

Now, I would like to use my NAS also as a network drive for my home's PC. I created shares, with user access permissions, I see for example the NAS on my windows explorer, but the transmission speed seems quite low while copying files. 

At home, we have about 5 PC's. I only need local shares

Before I search further, I have a question: Is this kind of service (both and simultaneous ftp access and network file server) correct for such a device? (RN102)

best regards