Just done a practice exam paper for physics unit 4 AQA and I'm totally deflated! Watch
I don't study your course. I do OCR Physics at A2. However, could I just ask that is this the first past paper you have done? Don't get downhearted. Just keep doing more past papers. The more you do, the more you understand exam technique. Practise makes perfect. The best students keep fighting!
The multiple choice is just something that you need to practice after careful revision of the knowledge. You can try to eliminate two answers that look wrong and go for a 50:50 if you can't answer the question. It's quite difficult, yes, but practice helps you get better at it.
I don't know what to suggest for the other section. Just make sure that you know everything.
For the test that you've already done, have a look at the paper again and see where you've gone wrong - whether it's exam technique, timing, exam pressure, or anything else. Figure that out and work on it.