Look into your system config by using service tag. There are two 8940 wireless options: Qualcomm vs Killer. Qualcomm much slower than Killer wireless card. Transfer rate Up to 433 Mbps  Qualcomm QCA9377 (DW1810) Up to 2400 Mbps  Killer AX1650i  
So the wifi on my dell XPS 8940 is running around 200mbs download 5ghz, while my 6 year old laptop is running at around 866mbs download, and they are in the same room. I have tried reinstalling the driver, unplugging and plugging in antenna cables, forcing 5ghz, and nothing has worked. Any suggestions?
XPS 8940, slow WiFi?