Recommend a book on mathematical calculation in senior high school.
The key is not how many questions you do, but to find and analyze the reasons for your mistakes in time, which is the key. Every time you make a mistake, don't just correct the answer, but also carefully analyze the reasons for your own mistakes, and strive not to make the same mistakes or make fewer mistakes next time. It doesn't matter how many questions you do. If you have time, do the wrong questions several times until you get it right, which is actually more targeted, effective and efficient. In fact, everyone is sloppy sometimes. As long as you have patience, you can reduce the chances of making mistakes, develop good habits of being careful and meticulous, and greatly reduce the possibility of making mistakes. Don't blame yourself too much, come on!