To become a Muslim, you must believe in Muhammad.
It’s impossible to become a Muslim without believing in Muhammad first. You cannot convert to Islam without adding the name of Muhammad to your profession of faith.
The shahadah says: “Ash-hadu an la ilaha illa Allah, Wa ash-hadu anna Muhammadan Rasulu-Allah.“
Translation: “I bear witness that there is no God but Allah, and Muhammad is the Messenger of Allah.”
The shahadah is the negation of the existence of the being called God. And it affirms a being called Allah, who is not God.
But no, by your Lord, they will not (truly) believe until they make you, (O Muhammad), judge. An Nisa Surah 4 :65.
