Bonus skills are extra skills that can be learnt, they cost a certain amount of lingots and will be available once purchased from the Lingot Store . They are currently only available in the five original languages, (Spanish, French, German, Italian and Portuguese.) There are four of them. (3 in the base languages, 1 in Chinese.) The Christmas bonus skill is seasonal but the rest may be purchased at any time. Once you have purchased them, you cannot get rid of them.