HI Team New to doing iphone App development, I need an easy way to calculate tax on a store. items being sold on an app. Any help or links would be great

After Xcode was updated to last 16 it no longer seeing my iphone 14 pro running ios 17.0 Any help on how to resolve this.

I am a bit new to app development, spent the last month or so doing an app that handles orders and I integrated the use of firebase as well as notification and apple pay. Now once the payment is done from the app, how do i know what the order is and where do i receive the money, Do i need to create mote handling for that or does it automatically come from apply pay ? Any pointers on this would be very helpful