How to convert program file into application file with .apk extension ?

Answer 1

means when we are making android app there is no need of programming language ?

Answer 2

you should know about android studio. and learn it. it's different from program you had

Answer 3

wrong. You need Android SDK package to develop Android apps, it based on Java. Android Studio is special tool to create mobile apps with plenty useful features to make your work easier.
Again, you need to know Java basics atleast (but it isn't enough) to develop Android apps