@XavierM 

If the wireless speed is not good as expected when connected to the extender, please refer to the below instructions to verify some basic settings:

What should I do if Internet/download speed is slow when the device is connected to the TP-Link Range Extender?

@Solla-topee No change, same low speed. I did all kind of test...Tried to connect to another router from a friend (800Mb --> 20mb with the RE455 ) False adverstiment? 

@XavierM 

Hello, it might be too early to say the adverstiment is false, please provide the information below so that we can do further analysis. 

1. What is the bandwidth you paid for your ISP? And what is the speed you can get from your modem or router directly?

2. What is the brand and model number of your main router?

3. How far away between the main router and extender? what about the signal strength?

4. With a computer connected to the extender, please check the wired speed and wireless speed separately. Then please show me the pictures of the test results.

Meanwhile, please check the wired/wireless link speed: https://www.tp-link.com/support/faq/2265/

5. To do a comparison analysis, please put your computer next to the extender and connect it to the main router to run the speed test and show me the result. 

Any updates, please let me know.

Thanks a lot.