Is someone who deliberately watches forbidden things on the internet, which causes him to miss the Maghrib, 'Isha, and Fajr prayers while sleeping without performing ghusl until sunrise, considered a disbeliever?

Delaying the prayer beyond its prescribed time is one of the gravest sins. The young man must repent to Allah Almighty, perform ghusl (definition), and make up the missed prayers. He should also marry if he is able; otherwise, he must fast, lower his gaze, and associate himself with mosques, circles of knowledge, and righteous people.