activity.recreate() inside fragment causes bottom navigation bar to stop working

I use 2 fragments inside my MainActivity, one is a preferences fragment and the other (default one) is a home fragment. I wanted to make sure that fragment doesn't get recreated if same item is selected in navigation bar. however now I have 2 problems:
1. If I try to change theme from my preferences the bottom navigation bar will stop working
2. Switching to preferences fragment doesn't change title in action bar but it should (I tested and it worked before implementing this the fragment replacement prevention . Here are some codes:
MainActivity.kt

class MainActivity : ThemeActivity() {

    private val homeFragment: HomeFragment = HomeFragment()
    private val settingsFragment: SettingsFragment = SettingsFragment()

    private var currentFragment: Fragment? = null
    private var activeFragment: Int = R.id.navigation_home

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        savedInstanceState?.let {
            activeFragment = it.getInt(CURRENT_FRAGMENT, R.id.navigation_home)
        }

        val toolbar: MaterialToolbar = findViewById(R.id.home_toolbar)
        setSupportActionBar(toolbar)

        val prefs = getSharedPreferences("prefs", MODE_PRIVATE)
        val firstStart = prefs.getBoolean("firstStart", true)
        if (firstStart) {
            showSecurityDialog()
        }

        when (activeFragment) {
            R.id.navigation_home -> currentFragment = homeFragment
            R.id.navigation_settings -> currentFragment = settingsFragment
        }

        if (savedInstanceState == null) {
            supportFragmentManager
                .beginTransaction()
                .add(R.id.frame_layout, settingsFragment).hide(settingsFragment)
                .add(R.id.frame_layout, homeFragment).hide(homeFragment)
                .show(currentFragment!!)
                .commit()
        }

        val navView: BottomNavigationView = findViewById(R.id.bottom_nav)

        navView.setOnNavigationItemSelectedListener{
            setFragments(it.itemId)
        }
    }

    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        menuInflater.inflate(R.menu.toolbar_menu, menu)
        return super .onCreateOptionsMenu(menu)
    }

    override fun onOptionsItemSelected(item: MenuItem) = when (item.itemId) {
        R.id.about -> {
            val intent = Intent(this, AboutActivity::class.java)
            startActivity(intent)
            true
        }
        else -> {
            super.onOptionsItemSelected(item)
        }
    }

    private fun showSecurityDialog() {
        AlertDialog.Builder(this)
            .setTitle("Welcome!")
            .setMessage("Before we implement a proper security system to check whether app was modified or not, please be sure that you downloaded manager from vanced.app/github")
            .setPositiveButton("close"
            ) { dialog, _ -> dialog.dismiss() }
            .create().show()

        val prefs = getSharedPreferences("prefs", MODE_PRIVATE)
        val editor = prefs.edit()
        editor.putBoolean("firstStart", false)
        editor.apply()
    }

    private fun setFragments(itemId: Int): Boolean {
        activeFragment = itemId
        when (itemId) {
            R.id.navigation_home -> {
                if (currentFragment is HomeFragment) {
                    return false
                }
                supportFragmentManager
                    .beginTransaction()
                    .hide(currentFragment!!)
                    .setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN)
                    .show(homeFragment)
                    .commit()

                currentFragment = homeFragment
            }
            R.id.navigation_settings -> {
                if (currentFragment is SettingsFragment) {
                    return false
                }
                supportFragmentManager
                    .beginTransaction()
                    .hide(currentFragment!!)
                    .setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN)
                    .show(settingsFragment)
                    .commit()

                currentFragment = settingsFragment
            }
        }
        return true
    }

    companion object{
        const val CURRENT_FRAGMENT = "current_fragment"
    }

}

PreferenceFragment.kt

class SettingsFragment : PreferenceFragmentCompat() {

    override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
        setPreferencesFromResource(R.xml.preferences, rootKey)

        (activity as MainActivity).supportActionBar?.title = getString(R.string.title_settings)

        val updateCheck: Preference? = findPreference("update_check")

       val themeSwitch: ListPreference? = findPreference("theme_mode")
        themeSwitch?.setOnPreferenceChangeListener { _, _ ->

            when (themeSwitch.value){
                "LIGHT" -> {
                    activity?.setTheme(R.style.LightTheme_Blue)
                    activity?.recreate()
                }
                "DARK" -> {
                    activity?.setTheme(R.style.DarkTheme_Blue)
                    activity?.recreate()
                }
                "FOLLOW" -> {
                    when (resources.configuration.uiMode and Configuration.UI_MODE_NIGHT_MASK) {
                        Configuration.UI_MODE_NIGHT_YES ->{
                            activity?.setTheme(R.style.DarkTheme_Blue)
                            activity?.recreate()
                        }
                        Configuration.UI_MODE_NIGHT_NO -> {
                            activity?.setTheme(R.style.LightTheme_Blue)
                            activity?.recreate()
                        }
                    }
                }
                else -> {
                    activity?.setTheme(R.style.LightTheme_Blue)
                    activity?.recreate()
                }
            }
            true
        }

    }
}

I tried to lookup on the web but couldn't find anything useful, I'm pretty sure the problem is with the activity recreation but I don't really know how to fix the issue.

Switched to Navigation Components. It's way better than manually making fragment transactions