What's the connection speed between the adapter and router? What's the operating system of your PC? Try to update chipmaker's driver. https://wikidevi.com/wiki/TP-LINK_TL-WN823N_v1 Try to install...

There is an instruction to configure bandwidth control. Just follow it to give a try. http://www.tp-link.com/en/article/?faqid=557

You can configure access control to forbidden some websites but https websites cannot be blocked.

How did you power off the router? Unplug the power adapter? Or press the ON/OFF button? Leave the Wi-Fi on, reset the router to factory default settings, power off the router and power it on. Now...

Download the one ( TL-WDR4300_V1_141113) from the link as below and ugprade your router. http://www.tp-link.com/en/support/download/?model=TL-WDR4300&version=V1#tbl_j

There is an answer to the similar question. http://forum.tp-link.com/showthread.php?79585-Obtaining-channel-14&highlight=japan