@MMAYUR89 

Good day.

Sorry for the delay.

Could you please tell me the hardware and firmware version on TL-WA850RE?

How far is the 850RE from the main router?

How long have you had the extender and when did the issue start？

If you had a wired computer, please also try to check the Ethernet speed from 850RE as well;

And please also refer to this link to check the wireless link speed on the Wi-Fi of 850RE https://www.tp-link.com/support/faq/2265/ ?

PS：Due to half-duplex system, “receive” and “send” cannot be carried out simultaneously. In that case, PC will get half speed of 300Mbps—150m/s; while considering the communication overhead, the actual download speed  is about half or a bit more than half of wireless associated speed in ideal situation, so the final download speed would be around 75m/s.

Thank you very much.