Firstly, I have Visual Studio 2019 Version 16.9.4 installed and have used it to build .exe programs designed to run on my laptop - so far so good

Over the years I have written a lot of code in VB6, VB.net, C, C++ and ASM (and FORTRAN on punched cards!)

I have also built a lot of websites using Notepad in HTML, CSS, Java Script and Classic ASP

I now want to build a website (no problem) from which users can access an app to download onto their mobile. The app needs to be able to tell me (with user consent, obviously) where the phone is geographically. I will then send them a message when certain events happen - possibly by email or Text or pop ups or whatever

Now for the problem - I still use a Nokia 6310i and am totally clueless on smart phones and apps!

So, I need to get a smart phone and then build the website (probably in PHP which I have a only a few hours experience of) and then build an app

So what smart phone should I get hold of?

How do I build an app using code (I want to be able to delve inside so I really do want to use detailed coding)?

All help very much appreciated and sorry if this is a dumb question(s) ...

Bob