"InJiltra" and "Ingiltra" are two variations of pronunciation and are both correct. While I and everyone I know would pronounce it "Ingiltra"- similar to its native "g" sound, other accents such as Egyptian would use the "J" pronunciation.
Both is possible. Found both options in my dictionary. But it's wrong -like Duolingo does- to write ,,injiltira" and say ,,ingiltra" or other way round, because what you said is obviously not what is written.