Now obviously I am not an expert or teacher but I usually get 12/12 on these questions and have got 9s in all my mocks and end of unit tests . I think this is probably a 6 out of 12. There is clear reference to religion, a consideration of different points of view and some evidence in support which is really good. The framework is there, now you just need to refine it a bit.
I think the key things to improve on here are structure and use of evidence. The structure seems a bit odd, as I don't see the value of the justification paragraph? It felt a little confused but I can totally understand if it was something your teacher made you do. If you want to start out the question with a sort of evaluation/introduction I would keep it short to allow time for the main bit of the question. Stick to knowledge and key facts: The lord's prayer is the most widely known prayer in Christianity and is said across most christian denominations- then add some key facts like it is was the prayer taught by Jesus to his disciples and it is used in religious ceremonies. INTRO DONE.
Then try to stick to a clear structure of 4 short paragraphs (2x for, 2x against) and then a reasoned conclusion. If you're finding the paragraphs hard to structure in themselves then: take your point (e.g. yes, it unifies Christians under one prayer), add some key facts/elaborate (e.g. it allows them to ask for their basic needs together) and add quotes in to support (so for the basic needs one you might say 'Give us this day our daily bread.')
You have used some quotes, which is great but I really think adding in some more quotes, particularly from the prayer itself would bump it up. Remember, in order to get 10-12 marks you need: A well-argued response, reasoned consideration of different points of view. Logical chains of reasoning leading to judgement(s) supported by knowledge and understanding of relevant evidence and information.
Overall, I think 6 out of 12 is pretty strong but in order to improve it might be worth doing some more questions but allowing yourself unlimited time to plan and write them, until you feel like you can do them with your eyes closed!