How can you save data to a file inside the Mobile Phone? Xamarin Android

Well, the question is that, what exactly i'm doing wrong?

i saw another similar post here about it, but none of them actualy help me to fix the issue.

here is the code:

AndroidManifest.xml (Permissions):

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="Notificaciones_Movil.Notificaciones_Movil" android:versionCode="1" android:versionName="1.0" android:installLocation="auto">
    <uses-sdk android:minSdkVersion="15" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <application android:label="Notificaciones_Movil"></application>
</manifest>

Methods involved in save and read data (Xamarin Android C#):

private bool JSONDesdeArchivo(out ItemLogin loginLogan)
        {
            //deserialize JSON from file
            loginLogan = null;
            bool isFileExisting = false;
            try
            {
                string JSONstring = File.ReadAllText(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal));
                isFileExisting = true;

                if (!string.IsNullOrWhiteSpace(JSONstring))
                {
                    loginLogan = JsonConvert.DeserializeObject<ItemLogin>(JSONstring);
                    return true;
                }
                else
                {
                    return false;
                }
            }
            catch (Exception ex)
            {
                if (isFileExisting)
                {
                    Toast.MakeText(this, "Something go wrong: " + ex.ToString(), ToastLength.Long);
                }
                return false;
            }
        }

        private bool JSONHaciaArchivo(ItemLogin loginLogan)
        {
            //serialize JSON to file
            try
            {
                //output JSON file
                string outputJSON = JsonConvert.SerializeObject(loginLogan);
                File.WriteAllText(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal), outputJSON);
                return true;
            }
            catch (Exception ex)
            {
                Toast.MakeText(this, "Something go wrong: " + ex.ToString(), ToastLength.Long);
                return false;
            }
        }

        private bool DeleteTextArchivo()
        {
            //serialize JSON to file
            try
            {
                //output JSON file
                File.WriteAllText(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal), "");
                return true;
            }
            catch (Exception ex)
            {
                Toast.MakeText(this, "Something go wrong: " + ex.ToString(), ToastLength.Long);
                return false;
            }
        }

Error that is showing to me:

{System.UnauthorizedAccessException: Access to the path '/data/data/Notificaciones_Movil.Notificaciones_Movil/files' is denied.
at System.IO.FileStream..ctor (System.String path, System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share, System.Int32 bufferSize, System.Boolean anonymous, System.IO.FileOptions options) [0x000f4] in <3fd174ff54b146228c505f23cf75ce71>:0
at System.IO.FileStream..ctor (System.String path, System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share, System.Int32 bufferSize, System.IO.FileOptions options, System.String msgPath, System.Boolean bFromProxy, System.Boolean useLongPath, System.Boolean checkHost) [0x00000] in <3fd174ff54b146228c505f23cf75ce71>:0
at (wrapper remoting-invoke-with-check) System.IO.FileStream:.ctor (string,System.IO.FileMode,System.IO.FileAccess,System.IO.FileShare,int,System.IO.FileOptions,string,bool,bool,bool)
at System.IO.StreamWriter.CreateFile (System.String path, System.Boolean append, System.Boolean checkHost) [0x0001c] in <3fd174ff54b146228c505f23cf75ce71>:0
at System.IO.StreamWriter..ctor (System.String path, System.Boolean append, System.Text.Encoding encoding, System.Int32 bufferSize, System.Boolean checkHost) [0x00055] in <3fd174ff54b146228c505f23cf75ce71>:0
at System.IO.StreamWriter..ctor (System.String path, System.Boolean append, System.Text.Encoding encoding, System.Int32 bufferSize) [0x00000] in <3fd174ff54b146228c505f23cf75ce71>:0
at System.IO.StreamWriter..ctor (System.String path, System.Boolean append, System.Text.Encoding encoding) [0x00000] in <3fd174ff54b146228c505f23cf75ce71>:0
at (wrapper remoting-invoke-with-check) System.IO.StreamWriter:.ctor (string,bool,System.Text.Encoding)
at System.IO.File.WriteAllText (System.String path, System.String contents, System.Text.Encoding encoding) [0x00000] in <3fd174ff54b146228c505f23cf75ce71>:0
at System.IO.File.WriteAllText (System.String path, System.String contents) [0x00007] in <3fd174ff54b146228c505f23cf75ce71>:0
at Notificaciones_Movil.MainActivity.JSONHaciaArchivo (Notificaciones_Movil.ItemLogin loginLogan) [0x00009] in C:\Users\Sincron\Documents\Visual Studio 2015\Projects\Notificaciones-Movil\Notificaciones-Movil\MainActivity.cs:260 }

Any question, suggestion, comment, request of clarification etc than you do would be greatly apreciated too if constructive and helps to find the answer.

Thanks in advance