Is Muhammed greater than Allah?

All scripture and prophesies before Muahmmed are corrupt unless they agree with the Qu'ran that was given to Muhammed. No prophets will come after Muhammed. Muhammed is not anounced by God and only bears record of himself.Allah can not speak only what comes from Muahmmed and with Muhammed dead Allah must shut up....Isnt Muhammed greater than Allah if Allah can only speak through him and now he is dead?