Fragments overlapping in Android

I'm trying to switch between fragments without losing the previous contents, so I decided to implement this way to do it:

private void loadFragment(Fragment fragment) {
    FragmentManager fragmentManager = getSupportFragmentManager();
    fragmentManager.beginTransaction().hide(fragment);
    if (!alreadyOpened[currentIndex]) {
        alreadyOpened[currentIndex] = true;
        fragmentManager.beginTransaction().add(R.id.fragment_container,fragment).commit();
    } else {
        fragmentManager.beginTransaction().show(fragment).commit();
    }
}

With this method I check if a fragment has been already opened: if yes, I show it, if not I add it. Then I declare it as "alreadyOpened". The problem is that when I switch between fragments I see all the three fragments overlapping. How can I solve it?
This is the menu bar when I invoke the loadFragment method:

private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
        = new BottomNavigationView.OnNavigationItemSelectedListener() {

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.bbn_item1:
                currentIndex = 0;
                loadFragment(new HomeFragment());
                return true;
            case R.id.bbn_item2:
                currentIndex = 1;
                loadFragment(new PopularFragment());
                return true;
            case R.id.bbn_item3:
                 currentIndex = 2;
                loadFragment(new PlayingFragment());
                return true;
        }
        return false;
    }
};

EDIT: new code

List<Fragment> fragments = new ArrayList<>();

private void loadFragment(Fragment fragment) {
    FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
    if (alreadyOpened[currentIndex]) {
        ft.replace(R.id.fragment_container, fragments.get(currentIndex));
    } else {
        fragments.add(currentIndex, fragment);
        alreadyOpened[currentIndex] = true;
        ft.replace(R.id.fragment_container, fragment);
    }
    ft.addToBackStack(null);
    ft.commit();
}

You should not created new Fragments on every navigation click. created once somewhere and save them in List<Fragment> fragments array. and after that use fragmentManager.beginTransaction().replace(R.id.fragment_layout, fragment); here is little example:

    FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
    ft.setCustomAnimations(R.anim.slide_in_left, R.anim.slide_out_left); //optional 
    ft.replace(R.id.fragment_layout, fragments.get(selectedFragment));
    ft.addToBackStack(null);
    ft.commit();

From your onNavigationItemSelected send selectedFragment variable, and match the position in the fragments list.

Edit:
how about this:

public HomeFragment homeFragment;
public PopularFragment popularFragment;
public PlayingFragment playingFragment;

private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
    = new BottomNavigationView.OnNavigationItemSelectedListener() {

@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
    switch (item.getItemId()) {
        case R.id.bbn_item1:
           if(homeFragment == null){ homeFragment  =new HomeFragment();}
           loadFragment(homeFragment )
            return true;
        case R.id.bbn_item2:
            if(homeFragment == null){ popularFragment  =new PopularFragment();}
            loadFragment(popularFragment)
            return true;
        case R.id.bbn_item3:
             if(homeFragment == null){ playingFragment  =new PlayingFragment();}
            loadFragment(playingFragment);
            return true;
    }
    return false;
}

};

public void loadFragment(Fragment fragment){
  FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
    ft.setCustomAnimations(R.anim.slide_in_left, R.anim.slide_out_left); //optional 
    ft.replace(R.id.fragment_layout, fragment);
    ft.addToBackStack(null);
    ft.commit();

}