If your using global variables, it would be reset every time you close your app or browser.
Use the webstorage plugin.
I assume you have a global variable for 'levels'. In this example, ill call it: Global_level
In your event sheet, input a condition on WHEN you want it to save the 'level'.
For example, On your level complete trigger (which is your condition), your action would be: Set local/session value (under WebStorage actions).
Here you would set: WebStorage.LocalValue("level")
Set local value "level" to (Global_level) (This would be your global variable but obviously you named it differently)
Now, when you are playing your game, and you complete a level, it would be stored locally in your device or pc. (Unless you clear cache).
Now, remember to get the local value from Webstorage "level" everytime you start your game so that it remembers which level you left off from.
So in your event sheet: On start of layout: set (Global_level ) to the Webstorage's local value. (Type in Webstorage and find LocalValue, It'll will look something like this: Webstorage.LocalValue("level"). Make sure to type level in between "" indicating the what string value to retrieve.
Hope that helps,