Basic question-where should I start?

Hey guys, so over the last month and a half I have been learning HTML, CSS, and Python. I want to take a little break from the more so “boring” part of learning them and maybe start playing around with some of the things I’ve learned.
My question for you guys is-Whats the best program to develop my app with?

There is no “best program”. We would also need to know a lot more about what the app is doing.

You posted under “Mobile App Development”. One path to take to mobile development is React Native, which is a flavor or React, which FCC teaches.

I guess there are also Python options like Kivy.