Android fragment get covered by another fragment

Using transactions I try to change a fragment in my Activity, but the previous fragment stays as where it was and a new one covers it:

This is how I change the fragments:

WorkoutDetailFragment details = new WorkoutDetailFragment();
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
details.setWorkout(id);
ft.replace(R.id.stopwatch_container, details);
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
ft.addToBackStack(null);
ft.commit();

How can I prevent it?

UPD: Here's acivity_main.xml file:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    android:padding="16dp"
    tools:context=".StopwatchFragment" >

    <fragment
        android:id="@+id/fragment2"
        android:name="com.example.workout.WorkoutListFragment"
        android:layout_width="160dp"
        android:layout_height="wrap_content"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <FrameLayout
        android:id="@+id/stopwatch_container"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintStart_toEndOf="@+id/fragment2"
        app:layout_constraintTop_toTopOf="parent">

        <fragment
            android:id="@+id/fragment3"
            android:name="com.example.workout.WorkoutDetailFragment"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </FrameLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

UPD2: I've found the solution. I just kept the fragment view nested in a frame layout. Instead, having used fragment transactions I added the fragment directly into frame layout in code.

How fragment terminology works:

getSupportFragmentManager()

This can be called from Activity or only using the reference of activity like
requireActivity().getSupportFragmentManager()

• This returns the FragmentManager for interacting with fragments associated with the activity.

getChildFragmentManager()

If you are in Activity : you cannot call this directly from activity or even using requireActivity()
If you are in Fragment : you can call this because it requires you to be in fragment. When you are in first fragment, now this becomes parent fragment. Now the parent fragment can have child fragments but activity cannot have child frgament.
These are usually seen when using ViewPagers or Nested ViewPager or in nested fragments.

• This returns a private FragmentManager for placing and managing Fragments inside of this Fragment.

I think we need not to write about getParentFragmentManager().

Let me start from activity container then.

activity_main

<FrameLayout
    android:id="@+id/stopwatch_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

</FrameLayout>

MainActivity

Please add transitions or back stack if needed.

I am calling getSupportFragmentManager() because we are in activity. If calling inside a fragment then differs.

WorkoutDetailFragment fragment = new WorkoutDetailFragment();
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction transaction = manager.beginTransaction();
transaction.add(R.id.stopwatch_container, fragment);
transaction.commit();

Now you are trying to call another fragment from WorkoutDetailFragment let's call HomeFragment

HomeFragment fragment = new HomeFragment.newInstance();
FragmentManager manager = requireActivity().getSupportFragmentManager();
FragmentTransaction transaction = manager.beginTransaction();
transaction.replace(R.id.stopwatch_container, fragment);
transaction.addToBackStack(null);
transaction.commit();

To call a fragment from existing fragment get reference to parent activity requireActivity() and call getSupportFragmentManager() upon it.