Country, person, language: じん and ご

じん means “person” and ご means “language”. Put them after a country's name and you have the word: にほん → にほんじん (a Japanese person) and にほんご (Japanese), スウェーデン → スウェーデンじん (a Swede) and スウェーデンご (Swedish). English also builds on the country's name, but changes the shape: Sweden, Swede, Swedish. Japanese changes nothing — it only adds. Two small endings cover every country there is.

The exceptions are languages that do not belong to a single country. English is えいご, so there is no アメリカご and no イギリスご — and no オーストラリアご either. The person still follows the rule as usual: アメリカじん, イギリスじん, オーストラリアじん.

Your country is not in the lesson's table? It is still the country's name plus じん or ご. Most countries outside East Asia are called in Japanese roughly what they call themselves or what English calls them, written in katakana: ノルウェー, フィンランド, ドイツ. Look your country up in the app's dictionary, add じん, and you have the word for yourself — add ご, and you have your language.