Aloha Sarlinda, I appreciate your essay. However, there are some thoughts I will share with you particularly understanding the question.
... people who stay in overseas after graduated for continuing their studies in 2002, 2006 and 2008.
this sentence is unsuccessful to paraphrase the question. Thus, you'd better pay more attention the question before starting to write your essay. Here is my sample paraphrasing;The bar chart gives information about the percentage of Bulgarian who prefer migrating to another country in the three selected periods (2002, 2006, and 2008) according to their education level.Levels of study program consist of elementary school or lower education, ...
I think this sentence is not needed in your essayOverall, the Bulgarian students who had graduated from junior high schoolpeople with secondary education are the highest number percentage of students whopeople planning study abroad than other graduates degreeto live abroad during those time. ThenAlso , the people who graduated...
in this question, it can be seen that the subjects who want to live abroad are people according to education level not students who are graduated