Export the project from Unity and opened by Android Studio

Hello everyone , I was export project from Unity and opened by Android Studio by follow steps:

• Export the project from Unity with the Google Android project checkbox selected.

• Open Android Studio:

• Go to File > Import Project. Choose a path (For example: If your project was exported to C:\MyProjects, pick C:\MyProjects\ path). Pick Import Destination Folder

• If it asks you to reload a project in the Language Level Changed dialog box, choose yes.

now, the project can run in Android Studio.But when Unity has some changes ，I export to android project again（step as above）, before the project is completely covered instead of merge,so I want to ask that is the export project can be combined ？thanks a lot...