who is your ISP? what is the speed you can get from it?

you can connect your computer to the C8 by wired cable and wifi separately to run the speed test and post the results. While do not forget to check the wired/wireless link speed, it is necessary. TP-Link has posted an instruction on how to get it: https://www.tp-link.com/en/faq-2265.html

right, the capacity of the wired device should be taken into consideration. 

Hello to all, thank you for the reply.

-About my wired device, it's a gibabit controller (Killer E2500).
-About my ISP. It's from Brazil, called NET. The wireless speed, that I informed before, it's the right one.

But I just checked my linkspeed at windows connections, and it shows 100 MBPS.

I will try to download newest driver from ethernet controller.

But, you guys point me to this direction, thank you. 
Post soon results.