I am learning backend but uses ai for my projects but everyone says that you should use ai for assistance don't use it to write code.

But I am seeing my friends making quite good projects in 15 days using ai where as here it takes me 1 week for setup and implement basic crud operations and auth.they always tells me to let ai write code if you are able to understand the code it's enough.

I want some insights from experienced backend developers who uses ai everyday.

How should I use ai should I write code by myself

Or let ai write it with being able to understand it.