@Camilo19 

It is suggested to update the Archer C5400X to the latest firmware released on the local website, then reset it to factory defaults and reconfigure it from scratch:

https://www.tp-link.com/support/download/archer-c5400x/#Firmware

If this doesn't help, please help verify some details and we will try to fix it together:
1. Without any devices connected, please connect one computer to the C5400X directly and go to speedtest to run the test for 3 times, will you be able to get the 1000M bps?
2. When you are referring to the wifi speed, are you talking about the 5G or 2.4G connectiion? What is the link speed when your phone or computer is connected to the network?

https://www.tp-link.com/support/faq/2265/
3. You can refer to the below instruction to narrow down the issue as well.
https://www.tp-link.com/en/faq-2170.html

Good day.