Thank you for your question. I understand you need to create an app for your website.
You can create a XAMARIN Forms application, add a web view control to your main page and load your website in it. Make sure your website is responsive, so it will display correctly in the mobile app.
Refer: https://learn.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/webview?tabs=windows
Hope this helps