Fig. 1 : Top-right language dropdown in stock TP-Link v11 interface (English/Română). Fig. 2 : System Tools → Language menu in classic interface. Fig. 3 : OpenWrt LuCI language selection page.
: Open a web browser on a device connected to the router and enter 192.168.0.1 or http://tplinkwifi.net in the address bar. Change Language in TP-LINK TL-WR841N -RO- v11.x
The "RO" in your model name often stands for a specific regional version (e.g., Romania). Change Language in TP-LINK TL-WR841N V7, How To 2 : System Tools → Language menu in classic interface
Dozens of languages via luci-i18n-* packages. Drawbacks: Requires technical skill; may void warranty; requires tftp recovery in case of failure. : Open a web browser on a device
You are likely logged in as a “guest” or with insufficient privileges. Log out and log back in using the admin account. If you forgot the password, reset the router (see below).