"Hanami" can be translated as "cherry blossom viewing", but if you simply say, "On Saturday, I did cherry blossom viewing," then a native speaker won't really understand you. They might wonder, "Did you view them from a bus? Was the goal to see as many trees as possible?"
To score highly on speaking tests like the G.B.C., you need to show the best of your English—make long but well-organized sentences, add detail, and show you have a wide vocabulary. One easy way to do that is to use comparatives.
In the G.B.C. exam, using advanced grammar and sophisticated logic will improve your score significantly. In this post, you'll learn a really simple trick using the relation between two tenses. With it, you can create longer and more complex answers.