Hi Simone;
Unfortunately at this time, PowerServer Mobile and thus AWS, do not support mobile App "file" functionality like you have in native PB Apps.
The only way I know of at the moment to achieve this would be to use a Cordova plug-in (which PS does support). For example:
https://cordova.apache.org/docs/en/latest/reference/cordova-plugin-file
Note that this Cordova plug-in example above is not built-in to AWS, so you would need to use the "Solution 2" approach as described in your PS Help (just search on the keyword "Cordova").
HTH
Regards ... Chris