android.support.v4.app.FragmentTransaction required

With getSupportFragmentManager() you are getting the supportLibrary fragmentManager instead of the systems fragmentManager. So you are working with a transaction of the supportlibrary.

This is the reason why you need to add all these imports and use android.support.v4.app.

If you want to get the systems fragmentManager just try to use getFragmentManager() instead getSupportFragmentManager().

Hope this helps

try this

public class DescriptionFragment extends android.support.v4.app.Fragment

instead of simply Fragment.