It sounds like you are having an issue with scrolling in a Flutter PWA (Progressive Web App) for the Telegram Web App. To fix the issue where the scroll affects the popup and the background content at the same time, you can try the following solution:

Disable scrolling on the main content when the popup is open.
You can achieve this by wrapping your main content inside a GestureDetector and setting its onVerticalDragDown and onVerticalDragUpdate callbacks to empty functions when the popup is open.

Here's a code snippet to help you with this:

dart
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import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  bool _isPopupOpen = false;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Telegram Web App')),
      body: GestureDetector(
        onVerticalDragDown: _isPopupOpen ? (details) {} : null,
        onVerticalDragUpdate: _isPopupOpen ? (details) {} : null,
        child: ListView.builder(
          itemCount: 50,
          itemBuilder: (context, index) => ListTile(title: Text('Item $index')),
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          setState(() {
            _isPopupOpen = !_isPopupOpen;
          });
        },
        child: Icon(Icons.add),
      ),
    );
  }
}
In this example, when you tap the floating action button, it toggles the _isPopupOpen variable, which disables or enables the scrolling on the main content.

Make sure your popup is using the Stack or Overlay widget.
To properly show a popup in Flutter, you should use the Stack or Overlay widget. These widgets allow you to overlay content on top of other content without affecting the layout of the main content.

Here's an example of how to use a Stack widget to show a popup:

dart
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// Inside the build method of your widget
@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(title: Text('Telegram Web App')),
    body: Stack(
      children: [
        // Main content (with scrolling disabled when the popup is open)
        GestureDetector(
          // ...
        ),
        // Popup
        if (_isPopupOpen)
          Positioned.fill(
            child: GestureDetector(
              onTap: () {
                setState(() {
                  _isPopupOpen = false;
                });
              },
              child: Container(
                color: Colors.black54,
                child: Center(
                  child: Card(
                    child: Padding(
                      padding: EdgeInsets.all(16),
                      child: Text('Your Popup Content'),
                    ),
                  ),
                ),
              ),
            ),
          ),
      ],
    ),
  );
}
In this example, the Stack widget is used to place the popup on top of the main content. The Positioned.fill widget ensures that the popup covers the entire screen, and the GestureDetector is used to close the popup when tapping outside it.

By combining these solutions, you should be able to fix the scrolling issue in your Flutter PWA for the Telegram Web App.