How to change the payment gateway to another ?

Hello,

 By mistake I selected Paypal as the gateway, instead of Paypal pro. I want to change this to paypal pro to this form. how do I do it ?

You can use the EDIT button in the Form Element / Payments to edit/delete the existing payment field.

Or you can just delete the current payment field using the delete icon when selected. You can replace it with another payment integration(field) then.