にほんごが　できますか。

Nihon-go is Japanese Language. [Nihon] means Japan and [+ Go] means language.
let’s think about Indonesia go = Indonesia + Language, It is easy structure.
Canada + go = Canada-go, America + go = Amerika-go ??? No!!
People can speak English in both countries. So English is ee-go in Japanese.
ex; Italy + go = Itaria-go, French + go = Fransu-go.
However Chines is Chuugoku-go, Korean is Kankoku-go.

Watashi wa kankoku-go ga dekimasu.
わたしは　かんこくごが　できます。
Chuugoku-go wa dekimasen.
ちゅうごくごは　できません。

Sydney Japanese Language School, Nihongo Juku gives you tips for your conversation in Japanese