I'm not sure how to answer the longer-answered questions e.g. those that are 6 marks.

This is a really common question that people ask actually and I struggled with this when I did GCSE. It's a good idea to jot down the points you want to include whilst you're learning how to answer these questions (in an exam situation you might not always have time). Usually if a question is worth 6 marks they will expect 3/4 main points for full marks so if you have those points you are on the way to a successful answer. Making up your own 6 mark questions is good practice and easier than you might think. Hope that helps!