Your first serve doesn’t matter if your second serve breaks down.
Here’s the exact second-serve progression: first on my own serve, then step by step with Kira (after 2 years of training).
Second Serve — My Explanation
Second Serve — Step by Step With Kira
Your second serve is the foundation of your service game. If it breaks down, you either play too safe — or you double fault under pressure.
Build it correctly first, and your first serve becomes much easier to use confidently.