Problem with android toolbar using navigation drawer

1. List the item

I'm developing an app using a navigation drawer and navigation components and I'm facing two issues:

I settled specifically each toolbar title where it is supposed to be, but every time I change the fragments, in the toolbar, for an instant, I can see the previous name from the fragment, which is the fragment name itself. So, it quickly changes from MySpecificFragment to MyFragmentName and I would like it to not happen. I've settled the title even onCreateView or onViewCreated. It didn't matter, still happening.
How could I decide the direction in which the back button of the fragment goes? I would like to create a standard position where the back button arrow goes, always the same. But it just travels back to the previous fragment (which is not a real problem, but I would like to improve its behavior)
Sorry for the lack of code, I don't know what I am supposed to display since I'm going against the standard android behavior.

P.S.: Using android studio and kotlin

Regarding the first issue, one way to avoid the brief display of the previous fragment name in the toolbar is to set the toolbar title in the parent activity and then update it from the fragment's onResume() method. This ensures that the toolbar title is set correctly when the fragment is resumed after being pushed onto the back stack. Here's an example code snippet:

In your activity:

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        setSupportActionBar(toolbar)
    }

    fun setToolbarTitle(title: String) {
        supportActionBar?.title = title
    }
}

In your fragment:

class MySpecificFragment : Fragment() {
    override fun onResume() {
        super.onResume()
        (activity as? MainActivity)?.setToolbarTitle("MySpecificFragment")
    }
}

Regarding the second issue, you can customize the back button behavior by using a custom NavController.OnDestinationChangedListener. In the listener, you can set the back button icon and its behavior based on the current and previous destinations. Here's an example code snippet:

class MyNavigationController(activity: AppCompatActivity, navController: NavController) {
    init {
        navController.addOnDestinationChangedListener(
            activity, object : NavController.OnDestinationChangedListener {
                override fun onDestinationChanged(
                    controller: NavController,
                    destination: NavDestination,
                    arguments: Bundle?
                ) {
                    if (destination.id == R.id.my_fragment) {
                        activity.supportActionBar?.setDisplayHomeAsUpEnabled(false)
                    } else {
                        activity.supportActionBar?.setDisplayHomeAsUpEnabled(true)
                        activity.supportActionBar?.setHomeAsUpIndicator(R.drawable.ic_arrow_back)
                        activity.supportActionBar?.setHomeActionContentDescription(R.string.back)
                        activity.supportActionBar?.setHomeAsUpIndicator(R.drawable.ic_arrow_back)
                        activity.supportActionBar?.setDisplayShowHomeEnabled(true)
                    }
                }
            })
    }
}

Here, you can adjust the back button icon and behavior based on the current and previous destinations by setting setDisplayHomeAsUpEnabled, setHomeAsUpIndicator, and setHomeActionContentDescription.

For both problems I've discovered the best approach solution.
The first, the problem containing the quick flash displaying the fragment name, it was caused by the label in the nav_graph file. When it's removed, the unwanted behavior stops. It was simple as that but took a long time to discover the cause, since it only happened to me using navigation drawer.
For the second, I tried to specify the button but it was not a good option. I was not able to clean the stack of fragments in the correct manner so my option was not editing the button functionalities, but instead of sometimes navigating back to the fragment, I choose popstackback, which I didn't knew yet. It helped a lot to avoid any unexpected behavior.
Hope it helps anyone.