This is the 2015th most frequent Korean word.
부분을
"부분을" means "part" or "portion" in English (object form).
The word "부분을" here is used as the object of the verb to signify the specific part or segment of 'the assignment' being acted upon.
과제의 중요한 부분을 완료했습니다.
I have completed the important part of the assignment.
"부분을" specifies which elements of the 'project' have been subject to review, conveying the idea of integral parts.
프로젝트의 모든 부분을 검토했습니다.
I have reviewed all parts of the project.
In this sentence, "부분을" denotes specific sections of 'the problem' that are intricate and challenging to comprehend.