My son is playing Nulls Brawl and he wanted to update a character like Kaze. But how to do it properly I have no idea yet. Can you give me some advice?

I think read our kids and themselves can figure out in such matters. The main thing is not to interfere with them and sometimes even listen to their words. But if for some reason your child can't find Update with Kaze, I recommend going to https://nulls-brawl.com/null-s-brawl-with-kaze-and-jae-yong-61-249/. I'm sure it's exactly what you need.