The system has a 10/100 Ethernet adapter, so it's not going to provide more than 100 Mbps.  If you want faster Ethernet speeds, there are plenty of USB 3 Ethernet adapters to choose from (the internal one cannot be upgraded;  it's part of the system board). Manual has the specifications: [URL]  
I have an Inspiron 5583 laptop, manufactured in late 2019. My wired internet speed (download) is 6x slower that my Inspiron 3647 tower (mfg in 03/2014)(adapter is Realtek PCle GBE Family Controller). I tested the tower (D/L 618 Mbps), then moved the same ethernet cable to the laptop (adapter is Realtek PCle FE Family Controller) and got D/L 96 Mbps. Both adapters have same settings, except that the tower has IPv6 checked, and laptop does not. Where do I start?
Internet speed