I am IT engineer but i am trying to design device which make device to device communication using usb. through this device i perform money transaction. but i dont know anythig about the electronics and i am new to microcontroller so please help me.
The best help is probably to get a consultant for the task.
Your request is too broad to be covered on a Keil-sepcific forum focusing on the use of Keil tools.
We can't cover what chip to use. We can't cover what external electronics. We can't cover what USB framework to use. We can't cover how to modify that framework. We can't cover how to debug your changes. We can't cover hot to productify your solution into a commercially sellable product.
If you are new to microcontrollers, you should do what everyone else have been doing. Learn to walk befure learning to run. Start with simple projects and gradualy increase the complexity.