You have 40 minutes for task 2, so try organising your time in the following way. Please note that these are suggestions, not rules.
First 10 minutes
Read the question and make sure you understand what it is asking you to do. Write a plan for a 4-paragraph essay (introduction, 2 main paragraphs, conclusion) and spend most of the 10 minutes thinking of ideas for the 2 main paragraphs.
Write your introduction: 2 sentences are enough.
Spend 10 minutes on each of your main body paragraphs. These are they most important part of your essay, and the key to a high score.
Last 5 minutes
Write a quick conclusion then check your work.