First, how to change the language back to English, video here.
Second, change the setting that has defaulted the language to change.
Go to Apps and click it. On a Magicsee N5 or N5 Max X3 tv box, the icon for Apps is not labeled. It’s the icon on the bottom right of the main screen of your tv box with 4 blueish/white squares.
Go to Droid Settings and click it.
Go to HDMI CEC and click it.
Go to Auto change language and click it.
This will toggle it off and should solve the issue of having the language default to something other than English.