lingua franca is not French, it was the language of the Franks, a Germanic language for a Germanic tribe. The French are a Celtic people (Gallic tribes) but their language derives from the Italic language of their Roman oppressors. If lingua franca interests you, Aryan roots and all, you should take a look at Anglish: as your English is quite good, it's a project that would be accessible to you to practice something much closer to lingua franca than French!