[Help] Flutter Dropdown

Hi All. This is my first time posting here, so pardon if this looks very messy. Below is my issue.

I want the the box dynamically fit the picked value, so it can grows bigger and smaller to fit its content.

Here is the box I mentioned:

The list of values:

How it looks like when each value picked:

Here is my code for review.

Is it possible with my code structure right now?

Please give me direction on what should I do to make it work (change widget is ok) or pointing me out where I did wrong.

Thanks a lot!