Learning to speak English fluently takes practice. My husband (an immigrant from Indonesia) started learning English by taking classes in high school and speaking regularly with English-language tourists in his home country. Then he came to the United States and studied at an institute like Language Studies International (that caters to teaching English to foreigners; http://www.lsi.edu/en/ ). After becoming a permanent U.S. resident, he continued his English studies at local adult schools. He is fluent now, but is still learning to improve his pronunciation even further. For some students, it can takes years of learning and practice to be fluent (and well-understood) in English.