how can i do that? im sure there are already payment methods or services that provided that. what i need is to read up on how i can create my own payment solution.
I don't think there's any detailed guide on how to create your own cryptocurrency payment gateway/processor out there. Although if you're serious about it, you can start by reading this documentation
https://developer.bitcoin.org/devguide/payment_processing.html.
here's a list of few
BTC payments process on GitHub.. But if you which to also go for altcoins then you can try out bitpay or CoinPayments those are the few reputable ones I can recommend for now...
That list isn't complete though. BitPay (which you've mentioned) and Coinbase Commerce aren't in the list, even though they're fairly popular option.