Some games autosave your progress when you're signed in with Google Play Games Mobile App. If your game autosaves, you can sync your game data and pick up where you left off. If you get a new Android phone, to restore game progress, sign in to the same account you used before.
Poki may give players access to loads of games, but its lack of info, questionable quality, and heavy amount of violence mean that only older gamers should take a look with parental guidance.