There are numerous ethnic Chinese in Brunei who speak Mandarin or another a Chinese language as well as numerous other ethnic minorities who have their own languages. English is the most commonly taught second language and many people, especially in the cities, have at least a basic understanding of English.
Religion
Muslim is the official religion of Brunei and nearly two thirds of the population adheres to this religion; nearly all of whom are ethnically Malay. The last third is almost evenly divided into Buddhists (primarily ethnic Chinese), Christians, and other belief systems, including indigenous belief systems.
Islam (the name of the religion, whose followers are called Muslims) is a monotheistic religion, whose holy book is called the Qur'an. The Qur'an is believed to be the word of God spoken through the prophet Muhammad from 609-632 CE (Common Era is preferred over AD (Anno Domini or "year of the Lord") since the Islamic world doesn't believe Jesus was the messiah). Islam believes Muhammad was the last prophet sent to earth by God, the last in a long line of prophets, which includes Moses, Abraham, and Jesus among others.
Muslims follow five pillars of their faith: testimony, prayer, alms-giving, fasting, and pilgrimage. These pillars, and other tenants of their faith, can give great structure to their lives as some foods, like pork, are forbidden and every Muslim is expected to pray five times a day. However, the level of participation in each of these pillars and to what degree Islam influences an individual's life varies from person to person and community to community. Generally speaking, Brunei has a mix of both liberal and conservative Muslims in how they practice.