@Unknownn 

Hi, thank you very much for posting on TP-Link Community.

1. You mentioned that you can get full speed when using wired connections, may I know if you mean wired connection to ISP modem directly, or wired connection to the router LAN port?

2. For the Wi-Fi speed of the router, you are connected to 5GHz WiFi, right? Please try disabling Smart Connect on Advanced->Wireless->Wireless Settings page and then change the 5G Channel&Channel Width to see if it helps.

3. May I know the brand and model no. of your wireless client device that used to test the WiFi speed? usually, how many client devices are connected to the router? and what are they?

4. Please make sure QoS is disabled

  @Unknownn 

Hi, thank you very much for the reply.

1. Please try running speedtest again on your iphone, and during the speedtest process, please check the Tx/Rx Rate(Mbps) between the router and the iphone on Network Map client list page.

2. Except for the iPhone, please connect a laptop to the 5G WiFi as well for comparison, please also run the speedtest at the same condition and check Tx/Rx Rate(Mbps) of the laptop as well.

After that, we would like to forward your case to our support engineer for further analysis via email.