Hi George! Those are really good questions. The answer to what programming language to learn is super subjective. I used more than 20 programming languages while studying, but today I'm mainly using Ruby by pure chance. But now I'm thinking about switching back to Python (I used it a lot in the past) because it's more on demand.

My decision is commercial, not technical, because I think Ruby can be better than Python in several aspects. But if you go to Google Trends, is easy to see how Python popularity is only growing.

Flutter is a framework for frontend, so you will need to learn how to create backends separately if you want to create an online store, and you can use a lot of tools for backend: Django, Rails, Go, Heroku, etc...

You have two options here:

1- Avoiding backend completely, so you can be a professional frontend developer.

2- Studying everything to become a full-stack developer.