How to answer session B questions (accounting standards questions)

You should find some useful guidance in the exam technique articles available at https://www.accaglobal.com/uk/en/student/exam-support-resources/professional-exams-study-resources/p2/technical-articles.html
The “guide to using the examiner’s reports” is a recent ACCA initiative which should certainly help you to get into the examiner’s head and what it is that he is looking for. And, even though this is your first attempt, you will find further details in the “guide to reflection for retake students”.
The single most important thing to do is “answer the Q set” – the candidate who can “think more – write less” is far more likely to succeed than one who “thinks less – writes more”. (It may seem a shame, especially when you have a good grasp of a topic, that you want to tell the examiner “everything I know about [topic]” – but he’s not interested in “knowledge dumping”.)