Dell XPS 9560 Ethernet Speed Maximum, Wifi Speed Maximum

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What network adapter? Check Device Manager. 

@duduckindy  The XPS 15 9560 doesn't have a built-in Ethernet controller.  If you have a USB Ethernet adapter, then the Ethernet controller chip is inside that adapter, so you'd be limited based on what the controller chip and the USB connection support.  But there are plenty of Gigabit Ethernet to USB 3.0 adapters on the market, and they're not expensive.  I'd look into one of those.  If you already have one of those, then check the network adapter properties to see the link speed being negotiated to your actual router.  Is it 1 Gbps or 100 Mbps?  If you're only seeing 100 Mbps even though your adapter supports Gigabit, then it could be an Ethernet cable or a problem with the adapter?  I had a Gigabit Ethernet adapter and once saw that it only negotiated at 100 Mbps, and the reason turned out to be that two of the pins inside the connector on the adapter had been pushed backward into the connector, so they weren't making contact. 100 Mbps only requires 4 pins, but Gigabit requires all 8, so once I opened up the adapter and fixed that, I had Gigabit again, so that could be your issue.

If you're seeing a 1 Gbps link negotiated with your router but still seeing slow Internet, then it could be an ISP issue.  The better test would be a speed test between devices on your local network in order to rule out the MANY variables that can come into play when testing speed over the Internet.