It sounds form your post that you have failed P3 a few times. I assume that you know the theories by now and that what’s giving you difficulty is answer technique. I think you should look for some sort of question-based revision course that concentrates on setting questions, having them marked and giving you feedback.
Try Googling ‘acca P3 question-based course’ and you will find some. For example, Kaplan seems to offer question-based days.