How to make cloud web application work offline like android

Question

Hi, We have a cloud based web application in angular 8 and asp.net mvc 5 and uses mysql as database. 

Currently, our application is online means it does not work without internet. User performs CRUD operations and that gets saved on cloud server and whenever required user gets data from cloud server for view purpose.

 

My problem is, some of our customers don't have internet. So how can i make my web application run offline also like android mobile applications does. Means i will save database locally and may be after every  30 seconds i will sync this local database to my cloud server MYSQL database.  Can i use sqlite for this?  and how to save data in local server and sync to mqsql database on cloud server.

Thank you all.