Diagnosing router network bottleneck

I have a weird network issue. I have the Bell Hub 2000 router and there seems to be a massive bottleneck.

If I’m transferring files from the NAS to my PC (tops out at 10 MB/s which is not normal) and try to download something at the same time (tops out at 1 MB/s, 8 MB/s without NAS transfer). The TV also begins to start stuttering.

It seems that all traffic is directed through the router.