When debugging a complex codebase, my approach would be to first try to reproduce the issue by recreating the steps that led to the problem. Once I have a clear understanding of the problem, I would start by reviewing any error messages or logs that were generated. This could give me some clues about where the problem is located in the code. Next, I would use debugging tools such as breakpoints and print statements to narrow down the location of the problem. I would also use the process of elimination, by commenting out sections of code to see if that resolves the issue. I would also look into the documentation and do some research on similar issues and solutions. Finally, I would seek help from my team members and ask for their perspective on the issue.
First read the answer fully, then try to explain it in your own words. After that, open a few related questions and compare the concepts. This method helps you remember the topic for a longer time and improves exam preparation.