Can you please refactor this dart/flutter code, fix code duplications and make it better readable if possible? You are allowed to rename, create, delete and combine functions as long as you don't change the functionality of the code. You are also alowed to extract code in seperate classes to achive this goals. This is the code you need to refactor:
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:tenmo/models/task.dart';
import 'package:tenmo/models/task_group.dart';
import 'package:tenmo/providers/navigation_controller.dart';
import 'package:tenmo/providers/task_groups.dart';
import 'package:tenmo/providers/tasks.dart';
import 'package:tenmo/widgets/others/list_headline.dart';
import 'package:tenmo/widgets/screens/task_screen.dart';
import 'package:tenmo/widgets/task_cards/task_card_for_backlog.dart';

class BacklogTasksView extends StatefulWidget {
  final int groupId;

  BacklogTasksView({
    required this.groupId,
  });

  @override
  State<BacklogTasksView> createState() => _BacklogTasksViewState();
}

class _BacklogTasksViewState extends State<BacklogTasksView> {
  late Timer _timer;
  DateTime? _currentDateTime;
  bool _selectMode = false;
  List<Task> _selectedTasks = [];
  late NavigationController _navigationController;

  @override
  void initState() {
    super.initState();
    _timer = Timer.periodic(
      Duration(seconds: 60),
      (timer) {
        setState(() {
          _currentDateTime = DateTime.now();
        });
      