Dear Fulgen, 

This is quite complex, task, but here is an idea of how you can do this. 

To add new action to the settings page you would need to create a new module and add it in the mobile application manifest to the CustomSchemas.

The code for adding custom action in the settings page is the following: 

Ext.define("Terrasoft.configuration.action.MyAction", {

    extend: "Terrasoft.core.action.AbstractAction",

    config: {

        myMessage: null,

    },

    execute: function() {

        this.executionStart();

        Terrasoft.MessageBox.showMessage(this.getMyMessage());

        var mainPageController = Terrasoft.util.getMainController();

        Terrasoft.Router.route("basepage", mainPageController, ["calleridsettingspageview", {direction: "left"}]);

        this.executionEnd(true);

    }

});

// Add action

Terrasoft.sdk.Application.addSettingsAction({

    name: "myItemName",

    caption: "MyMobileCustomSchemaTestActionCaption",

    actionClassName: "Terrasoft.configuration.action.MyAction",

    actionClassConfig: {

        myMessage: Terrasoft.LS["MyMobileCustomSchemaTestActionMessage"]

    }

});

MyMobileCustomSchemaTestActionCaption and MyMobileCustomSchemaTestActionMessage are 2 localizable strings. 

After that you can look what does the onChangePasswordClick in the ChangePasswordModuleSchema schema and implement the same logic in mobile when clicking your action. For changing language you would need to display lookup column of SysCulture object and populate the current user's culture with the result of the selection of this field.