As a new user I suggest to read through the documentation on the mendix website.
This might be a good starting point to find your answers:
Microflows get executed on the server so you cannot save data in the client from a microflow (as far as I’m aware, not quite sure about mobile). You can try executing the call in js/jQuery and save the data in the browser local storage or cookies.
Edit: If you’re planning to run with the client execution you I suggest to use the HTMLSnippet widget, as for examples for storage W3Schools are your best sources for examples ( https://www.w3schools.com/html/html5_webstorage.asp and https://www.w3schools.com/js/js_cookies.asp )
Hope this helps.