Hello, wanting to study in depth is generally is good habit, but when it is deviating you from studying the important things that you should be studying, it can become a problem. From what you've told me, it's seems that you are subconsciously avoiding the task at hand by giving the excuse that you want to study the basics first. This is what we call a "defense mechanism". Also, there may be an issue of procrastination. Both of these issues can be resolved by counselling and psychotherapy.
Next Steps
Take an appointment with counselling psychologist.