It depends on the guidelines of the university where you taking that course. But normally Master's dissertations are conducted individually under the close supervision of your professors.
Individually of course! You can discuss with your peers, brainstorm but better write it yourself. Concepts may match but writing pattern and style vary. Besides, you will be guided by your supervisor and faculty members, so ace it individually.
individually preferably. sharing ideas and understanding the ideas of your peers for the purpose of understanding further and adding to the existing knowledge its ok, however i personally believe that, writing alone gives the researcher a better opportunity to express their own views and input on the topic at hand.