hello there!
i have a question, maybe someone has insights. which program language the best decision for automation testing (gathering opinions for new article).

thank you!

Highly depends on everything.

You don’t just make script kiddie test files.

Also depends on what kind of frameworks / testing you will be doing example : web, mobile, api, unit, security, performance.
IMO you can start with java as it has solutions in each field.
Python is another language you can pick up.
Robot Framework (my favourite) is a cool framework developed in python can help with many form of testing mentioned above with basic functions created in terms of keywords so you can start automation in plain English.
Javascript is another language people use for testing I haven't used it much.

If you are doing unit testing then your language is the one the application is built on.