In this example, the main verb is ‫أحب‬ [like] and the negation particle depends on the tense of the verb ‫ل‬ for the present, ‫لم‬ for the past and ‫لن‬ for the future.
actually, it is true that there is a common language that is understood by the majority of educated arab people because it is taught at schools and it is the main language of the media in most arab countries.