've noticed that I often struggle with problems in the Codeforces style, and my coding ability is very weak. Others can finish writing the code in 15 minutes, but I spend an hour debugging it. Could anyone please give me some training methods or problem lists that are worth learning from? I would really appreciate it.

In the contests I participated in before, I felt they had a lot of depth in thinking and the problems were interesting. But nowadays, the problems are all classic and only test coding ability. So is this because Codeforces' review process has become more lenient?