"Estonia, the Estonian language, and an Estonian person"
Translation:Viro, viro ja virolainen
That is true IF you are using the word "kieli" after it (but it should not be capitalized).
"viron kieli" = the Estonian language
"viro kieli" is indeed incorrect.
But another way to say it is simply "viro". In that case you do not use the genitive (possessive) form. In other words, "viron kieli" is another way of saying "viro" and both mean "Estonian language".
Also: With a capital V, "Viro" means Estonia. With a lower case V, "viro" means the Estonian language. The phrase "viron kieli" also has a lower case V.