Belgium - but only in the capital - Brussels (Brusel (Flemish), Bruxelle (French)). In Flanders, Flemish is the official language, whereas in the Walloons, French is the official language. Because of...
La langue française (because the word "language" is feminine). Française is the feminine form, and if you're describing a masculine noun, the adjective would be français, without the "e". If you...