Follow below step & Image snap to Return back Customers to Website after payment done using Paypal
1 Log in and click the Profile subtab under My Account.
2 Click the My Selling Tools
3 Website Payment Preferences
4 Click the On radio button to enable Auto Return. Enter the Return URL. Note: You must meet the Return URL requirements in order to set up Auto Return. Learn more about Return URL.
5 Click the On radio button to Payment Datat Transfer
Source : Paypal