@Smok37  Hello, 

You could try a different Wi-Fi channel on the main router, and try 2.4Ghz channel width 40Mhz for higher speed and set wireless mode as 802.11n. 

Please scan for Wi-Fi channel using Wi-Fi analyzer APP or software and select a relatively idle channel for 2.4Ghz. 

Here is a chipset driver for  TL-WN823N V2,, please give it a try 
https://static.tp-link.com/2019/201911/20191129/Driver_RTL_8192EU_TL-WN823N_V2.zip
 
Here is an instruction to manually install driver:  https://www.tp-link.com/support/faq/920/

If still the same issue, may I know the model of router and can I have a photo of the wireless settings?

Can you share me a photo of speedtest results the wifi Link speed of adapter:

https://www.tp-link.com/support/faq/2265/

At the same location, can you test speed on another laptop or phone and share the speedtest result sna dlink speed?