First thing I would do is work to isolate the problem. Turn off your WiFi on the PC, then plug your PC directly into the TP-Link router and check your speeds there. If as fast as you expect, then disconnect from the router, renable WiFi on your PC, and check your speed directly to the router. Again, if OK, then is sounds like the range extender might be maxed out. If slow, like originally via the extender, then the TP-Link WiFi router or settings are off.
I had a slow link through a TP-Link router. Problem turned out to be I had used an old CAT5 cable to link the internet modem to the router, and it couldn’t handle the higher speeds that both the modem & router were capable of. I separately had a problem with a router setting, where I had bandwidth controls set, and they weren’t high enough to support the higher data-rates the other gear was capable of - effectively throttling speed down.
Agreed....he needs to make sure he has a CAT6 cable not CAT5e.....
Cat6 supports data transfer speeds up to 10 Gbps at 250 MHz with even less (or no) crosstalk interference, due to the cable’s improved insulation. However, its 10 Gbps speed is effective only up to 164 feet. Despite this limitation, Cat6 cabling is more qualified to handle the fast pace of Gigabit Ethernet networks.