Connection stability issues Nighthawk AX1800 USB Adapter

Hi, 

I from France and just bought an adapter USB the Nighthawk AX1800 WIFI USB (A7500) . I constantly encounter problems with my connection. My wifi is very slow especially in games. I tought it could came from my router but there is no problem with my phone, ipad or TV. I start thinking that my adapter might be defective. 

anyone have a solution ? 

thx 

Nico