After a test I can see my wrong answers, but I am not sure what to note down. Should I write the full solution again or only the trick?

When I practice normally my answers are mostly correct, but in timed practice I make silly mistakes. How should I reduce this?

I am trying to improve my solving speed for school tests. If I solve too many questions in one day, I forget the explanation. What is a practical daily target for Class 7 practice?