I need to share specific part in my app when user open it , if he download my app it navigate direct to this part (it may be nested fragment).
String AppURL
As mentioned by @Ragu Swaninathan, you can use ShareLinkContent from Facebook SDK.
Now to achieve the redirection to the specific screen of the app, you can use Firebase dynamic link feature. You can generate dynamic links using Firebase SDK and then receive those links in the app to handle the navigation flow. You need to share these dynamic links along with the contents.