About your footpiece, probably 'sina toki kepeken toki Epanja' "You speak Spanish", not "You are the Spanish language" as you wrote.
x is a velar fricative,which offers the choice of a velar sound, k, or a frictive s. Sonja chose s, possibly influenced by the fact that it was until recently pronounced sh and still is in parts of Mexico. The argument for k is a good one but lacks side argumentsother than English usage, which struggle to avoid.