For the first question regarding the sentence "Ayer compré el jabón," the direct object "el jabón" (the soap) is masculine singular. Therefore, the correct direct object pronoun to use in place of "el jabón" is "lo." The correct sentence would be "Ayer lo compré."
For the second question about the main purpose of the Cartagena Film Festival, the correct answer is: to promote Ibero-American cinema.