Why is the wi-fi download speed low in Upvel UR-325bn?

Question

WiFi

Good afternoon. Connected to Beeline via L2TP. The speed over the cable directly from the provider and through the LAN ports of the device corresponds to the declared one, but over WI-Fi it is 3 times lower. I changed the channel, flashed the firmware. Worth the latest stable version. There are not many devices used, the walls are thin.
It seems to me. that this is not a very normal situation, help me figure it out, please.

Answer 1

Something is missing here, numbers and equipment models and what connection standard is used for Wifi