How to negotiate and fully understand the salary structure?

My first job switch:

I recently got cleared of an interview and received an offer. I asked for a 40% raise knowing that it would eventually be reduced in negotiations. After a few calls, the recruiter made me agree for nearly 30% but fully fixed CTC.

But on receiving the salary breakup on email, it seems like a major portion of the 30% hike goes into performance pay which is approx 3 lpa. I demanded an explanation on email about the breakup. The recruiter instead called and confirmed there is no variable pay but they can't reply on email as they are very busy.

The recruiter also rudely said that I can either accept or decline the offer letter. But until the offer letter is released I should reply on email stating I'm fine with the breakup shared.

Questions: How can I convince the recruiter to what is discussed on call to reply on email?

How does this process normally go?