Hey, I was wondering if I could get some help here.

I have a little bit of a more advanced network setup.

I have a edgerouter PoE connected to gig fibre.. I get great speeds > 900mbit, so no problems with the internet.

One of the ports powers a nanostation M5, and points to my sisters place next door, in her place i got a mikrotik as her router, so she gets just over 100meg internet for free (because i pay for it).

Anyway Port 1 on my PoE router plugs into a 16 port gig unmanaged switch (its a little bit old) but i got all my ethernet port jacks in the wall coming back to it and on any of these ports in the house if i plug a laptop or pc in and do a speed test I get a solid 900mbit which is fantastic. Wifi is 300mbit + so no wifi issues.

Here lies the problem. I only have 1 spare ethernet port in my office. And since I been working from home and have a few pc's I need multiple connections in there for the time being im using wifi but ideally I want to have a few devices in my office plugged in via ethernet. 

So i purchased a 5 port desktop (cheap and nasty) unmanaged switch from pbtech. On its own this switch is fine but if I hang it off a port on my 16port switch it does all sorts of funky stuff and drops out etc. 

So i tried creating another network and plugging into the switch directly. but that means the routers cpu has to process all the packets and the performance is a bit poo.

DO i need to replace this 16 port switch to get this setup working ideally? I dont think its the cheap 5 port office desktop switch i tend to think its the main one but I dont know why its a bit crappy..

Any advice?