Help with android studio various activitys, obtaining data

I have a program of 2 activities, the initial activity is a log that connects to a bd by remote control, establishes the connection if the user and password are correct.

Now in activity two I need you to show me in a TextView the name of the user that started the session. How do I do that?

I leave part of the code here to give you an idea:

Activity 1 all right works included exceptions and connects to the bd

public class MainActivity extends AppCompatActivity {
    Connection conn;
    Button btnlogin;
    EditText euser,epass;
    TextView tuser,tpass;
    String[]usuarios;
    String CUsuario;
    String Pwd;
    Boolean prueba=false,prueba2=false;
    SharedPreferences sharedpreferences;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btnlogin = (Button) findViewById(R.id.BtnAceptar);
        euser=(EditText) findViewById(R.id.TxtUsuario);
        epass = (EditText) findViewById(R.id.TxtPassword);
        tuser = (TextView) findViewById(R.id.TextView01);
        tpass = (TextView) findViewById(R.id.TextView02);

        btnlogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Pwd= epass.getText().toString();
                CUsuario=euser.getText().toString();
                Login tarea6=new Login(euser.getText().toString(),epass.getText().toString());
                tarea6.execute();
            }
        });
    }

    private class Login extends AsyncTask<String, Integer, Boolean> {

        public Login(String usuario, String contraseña) {
            super();
        }
        @Override
        protected Boolean doInBackground(String...usuario) {
            conn = DBConnection.getInstance().getConnection();
            try {
                prueba = false;
                prueba2=false;
                String stsql = "SELECT CUsuario,Pwd FROM dbo.xUser WHERE CUsuario='"+CUsuario+"' or Pwd='"+Pwd+"'";
                Statement st = conn.createStatement();
                ResultSet rs = st.executeQuery(stsql);

                    while (rs.next()) {

                        if(CUsuario.equals(rs.getString(1)) && Pwd.equals(rs.getString(2))) {
                            prueba = true;
                            CUsuario = rs.getString(1);
                            Pwd = rs.getString(2);
                        }
                        else if(CUsuario.equals(rs.getString(1))) {
                            prueba2=true;

                         }
                        }
                }catch (SQLException e1) {
                e1.printStackTrace();
            }

            publishProgress(100);
            return true;
        }
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }
        @Override
        protected void onPostExecute(Boolean aBoolean) {
            super.onPostExecute(aBoolean);

            if (CUsuario.equals("") || Pwd.equals("")) {
                Toast.makeText(getApplicationContext(),"inserta un usuario y una contraseña", Toast.LENGTH_SHORT).show();
                euser.setText("");
                epass.setText("");
            }

            else if (prueba==true) {
                Toast.makeText(getApplicationContext(), "acceso permitido", Toast.LENGTH_SHORT).show();
                euser.setText("");
                epass.setText("");
                Intent siguiente = new Intent(MainActivity.this, Main2Activity.class);
                siguiente.putExtra(CUsuario, euser.getText().toString());
                startActivity(siguiente);
                prueba=false; 
            }
            else if ((prueba == false)&&(prueba2==false)) {
                Toast.makeText(getApplicationContext(), "contraseña y usuario incorrectos", Toast.LENGTH_SHORT).show();
                euser.setText("");
                epass.setText("");
            }else{
                Toast.makeText(getApplicationContext(), "usuario correcto,contraseña incorrecta", Toast.LENGTH_SHORT).show();
                epass.setText("");
            }
        }
        @Override
        protected void onProgressUpdate(Integer... values) {//este es para interactuar con la interfaz grafica mientras esta en ejecucion la tarea asyncrona
            int progreso = values[0].intValue();
        }

    }

Activity 2

public class Main2Activity extends Activity {
  Button btn1,btn2,btn3;
    public TextView t1;
    Connection conn3,conn;
    String[]llamadas;
    int IdLlamada;
    Date Fecha;
    String Mensaje;
    String De;
    String IdUsuarioDestino;
    String NombreUsuario;
    String CUsuario;
    boolean Estado;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        t1=(TextView)findViewById(R.id.t1);
        btn1= (Button) findViewById(R.id.Btnllamadasatendidas);
        btn2= (Button) findViewById(R.id.Btnllamadasperdidas);
        btn3= (Button) findViewById(R.id.Btncerrar);
        NombreUsuario=getIntent().getExtras().getString(CUsuario);
        Intent intent = getIntent();
        String user= intent.getStringExtra( NombreUsuario);
        t1.setText(user);

I think the bug is in the username in the CUsuario it does not let me get the EUser of the other activity and pass CUsuario and it's empty, any solution?