Nighthawk C7000 Slow Upload speeds on Laptop

I have Spectrum 100Mbps internet.  I was using Spectrum's Technicolor DPC3216 modem which was giving me 100+Mbps connected through ethernet cable.  I purchased the Netgear C7000 and installed.  On laptop, I can now only get about 35-45 Mbps with either ethernet or WiFi.  It makes no sense since I was getting 100+Mbps on the laptop with the Technicolor modem through ethernet cable.  But now I can't even get 50Mpbs with the Netgear C7000 modem with ethernet cable.  I have done a factory reset on the modem which improved nothing.  From the moment I installed the C7000, I have never seen more than 35-45Mbps.  I have no clue what do to!  Very frustrating!  Anyone with advice??