Best way to achieve Offline functionality in Ui5 app in 2020

I have created Mobile version of my Ui5 through HAT, now i want to add offline functionality in that app.

1. On Main page of app i am applying filters and loading data with service call. On click of download button I need to store that data offline. And want to perform CUD operations.

2. When internet is present i need to click on Sync button to perform all service calls.

Which is the best way to achieve it ?