1.To my mind, the main reason people leave their home countries is that they want find a better life in another one. However, there other cases. For example, a person should move to the USA to work in a big company or to marry with another person.
2.I think, that they face a great number of problems. It can be the absence of work and accommodation, bad relationships with citizens of country and their stereotypes, and others.
3.I don't wanna live in another country. I believe, that in the future me and my generation can make a great difference, develop and improve the life in my country.