Here is the workbook I created while preparing for the Qiskit Certification exam. I followed the official guide by James Weaver and tried to cover most of the topics which come up in the exam. I decided to leave out the explanation of basic concepts in Qiskit as they are best described in the first two chapters of Qiskit Textbook. At the same time, I have put more attention into rather advanced concepts which were new to me. I have separated the exercises and the solutions in my workbook so that you can test your skills at the end of each chapter and compare with my solution later.
I'll be glad if you find this workbook useful. Once you go through it, I suggest you make a textbook of your own in the same manner. What is a better way to learn something than to explain it in a written form? :)
Certainly, take a look at the official study guide. Another excellent workbook was created by Bartu Bisgin and goes through slightly different topics. There is another helpful and extensive workbook by Dimple M., which goes through every section in detail.
You are most welcome to contact me for feedback or improvement suggestions.