Should the worshiper say, "We seek help from Allah," if he hears the Imam say, "You alone we worship and You alone we ask for help" during prayer?

The congregant must listen attentively to the Imam's recitation and should not engage in anything else besides reciting the Fatihah. The saying of some congregants, "We seek Allah's help," or repeating the verse: (It is You we worship and You we ask for help) upon hearing it from the Imam is a forbidden innovation (bid'ah). This is based on the Almighty's saying: (And when the Qur'an is recited, listen to it and pay attention that you may receive mercy), and because the congregant's saying "Amin" after the Fatihah is sufficient.