Structure your preparation based on your timeline:
weeks: Focus on framework (Section ), core concepts (Section ), and - design problems. Skip advanced topics.
weeks: Add building blocks (caching, databases, queues). Practice - design problems.
+ weeks: Cover everything. Practice + designs. Do mock interviews.
For each design problem, first attempt it yourself for minutes. Then review the solution. Identify gaps in your knowledge. Study those building blocks. Retry the problem a week later.