It's good to know how to reflect. The most important thing now is to analyze the reasons for your mistakes. If carelessness is wrong, it proves that you have not studied hard enough and need to correct your learning attitude. If the basic knowledge can't, then you should systematically review this part of knowledge. Don't worry, the assembly part is actually not difficult. Grasp the basic knowledge points, read more typical examples and practice systematically. I believe you can. Let's go