Hello, there are two main approaches: negotiate with each system (credit cards, online banks, electronic wallets) separately or connect to an aggregator (concentrator) of payment systems. The choice depends on what you need and on what conditions you want to work. If you want your own conditions, special privileges, or you have requirements that payment service concentrators cannot fulfill, then you should negotiate with each payment system separately. This will take a lot of time and will not be cheap, but it is possible to save your resources in the long run. Thus, the processing credit cards will be safer and faster for your customers.