My professor wanted me to write a short summary (one or two paragraphs max) on each paper. Focus on the salient of the method. could I use the abstract sentences exactly or should I change the words and write with my own words? I was wondering if you could tell me whether it is necessary to read whole the papers or it is enough to read abstract and conclusion part?
He has asked you to write a summary of the works. I expect he wants to assess how you write, as well as your understanding of the papers themselves.
Copying the abstracts verbatim not only obstructs this goal, but is also plagiarism. The ideas and words are not your own and you should not try to pass them off as such.
Read the papers carefully and summarise them in your own words.