Nested Fragments doesn't back to the previous one

Question

In main Activity I show new DialogFragment which is ParentFragment with only 1 frameLayout in it. From this fragment i add new Fragment into frame layout. (Fragment A)

val fragment = GetCheckQrChildFragment.newInstance()
        childFragmentManager.beginTransaction()
            .setPrimaryNavigationFragment(fragment)
            .add(R.id.container, fragment)
            .commit()

From the GetCheckQrChildFragment i can replace a fragment too (Fragment B)

val fragment = GetCheckChildFragment.newInstance()
fragmentManager!!.beginTransaction()
                .setPrimaryNavigationFragment(fragment)
                .replace(R.id.container,fragment)
                .commit()

But if i press the back button from the last Fragment B it doesn't return me to Fragment A. It returns me to activity from i show Dialog Fragment. How can i return from Fragment B to Fragment A?