Is this from a mock or your actual GCSE exam? if it was your actual exam you can get your paper remarked or ask to resit the exam. If it was a mock you can improve easily by doing exam questions and get your teachers to mark it for Q5 you can do short practise paragraphs and review them and to get inspiration for your Q5 responses you can look at short stories online to help you get an idea of the format. Was It any question in particular that let you down?