[autokad]

I think the OP's 'problem' is that they do not sit down and have focused practice properly. They are not good at coding interviews, they were not good at math, and freely admits they "didn't study at all". You get really good at things by practicing them a lot, especially math and leetcode. It's not a criticism, as I am terrible at coding interviews and I can never muster the discipline to sit down and study it. However, its not because I am just innately bad at it, its because I don't practice it.

Amadeus was probably more fiction than it was a true story. Mozart practiced a lot.