Hello Solehan Zakaria,
I went through your app, and I found that you are using a normal Database that saves data on the server.
If you wish to store data locally you have to use Local Storage.

Once you create a local storage database entity as shown in the image above, you will have database actions to CRUD data.

You can refer to Mr. Bruno Cantante's answers for more details to know more about local storage and how to use it.
Best Regards,
Riyas