What did i do wrong in my understand of save data, need to make an easy app for adding to numbers together and save the result for adding more to it - sharedpreferences

Question

package com.example.application.myapplicationenter code here
import android.content.Contextenter code here
import android.os.Bundleenter code here
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
var c = Antal.text.toString().toInt()
val MY_PREFS_NAME = "MyPrefsFile";
val editor = getSharedPreferences(MY_PREFS_NAME, Context.MODE_PRIVATE).edit()
editor.putString("name", "Elena")
editor.putInt("idName", 12)
editor.apply()
val prefs = getSharedPreferences(MY_PREFS_NAME, Context.MODE_PRIVATE)
val name = prefs.getString("name", "No name defined") value.
val idName = prefs.getInt("idName", 0)
Navn.text = name.toString()`enter code here`
Alder.text = idName.toString()
button.setOnClickListener {
val pref = applicationContext.getSharedPreferences("MyPref", Context.MODE_PRIVATE)
var a = Antal.text.toString().toInt();`enter code here`
Alder.text = pref.edit(a + c)`enter code here`
}
}
}