Bottom Navigation Bar is getting removed after switch fragments

Question

The Bottom Navigation Bar is getting removed after coming back from a fragment which has visibility none for the navigation bar. What to do

This is the fragment in which the bottom navigation is removed

 activity?.findViewById<BottomNavigationView>(R.id.bnb)?.let {
            (it.parent as ViewGroup).removeView(it)
        }

This is main activity

bottomNav.setOnItemSelectedListener setOnNavigationItemSelectedListener@{ item ->
            when(item.itemId){
                R.id.btn1 -> {
                    supportFragmentManager.beginTransaction().replace(R.id.nav_host_fragment_content_main, btn1Fragment()).commit()
                    return@setOnNavigationItemSelectedListener true
                }
                R.id.btn1 -> {
                    supportFragmentManager.beginTransaction().replace(R.id.nav_host_fragment_content_main, FirstFragment()).commit()
                    return@setOnNavigationItemSelectedListener true
                }
                R.id.btn2-> {
                    supportFragmentManager.beginTransaction().replace(R.id.nav_host_fragment_content_main, btn2Fragment()).commit()
                    return@setOnNavigationItemSelectedListener true
                }

                else -> false
            }
            true
        }