Few non-native Tajik speakers in Tajikistan learn Tajik, but instead often learn Russian in addition to their native language. Russian is perhaps the most common language of communication across ethnic groups and many industries rely heavily on Russian. English and other popular international languages are rarely learned in Tajikistan although some young people are choosing to learn these languages, with English (after Russian) being the most popular.
Religion
About 85% of the population of Tajikistan is Sunni Muslim. Another 5% of the population is Shia Muslim with the last 10% comprising numerous other religions.
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, Tajikistan is fairly liberal in how they practice Islam.