I'm too new for this

Nice to meet you all, I hope you guys can guide me on something cuz I want to try but scared of whatever brick/mistake I could do in the future.

I have a Redmi 12 since 2 years ago, and HyperOS had my phone laggy since then, each update is more weight into my phone performance and I want to change that, so I've been looking up some CustomROMs and some of them are pretty decent and fast.

But most of them doesn't count with something that I use to much, and it's something about the payment methods? Like, bank payments, Paypal, etc, which probably it's not possible...? I don't know, I've seen that often and I don't want to sacrifice my phone like that.

Can you guys help me in it, or just give me some tips, any solutions for it?