Saving with PlayerPrefs? How it works?

I would implement save-games using some kind of serialization, not using PlayerPrefs. PlayerPrefs saves values to either the registry on windows, or a plist file in your library folder on MacOS. Saved games are likely to be too large, and use too many data types which are not compatible with the preferences, that it would be impractical to use them. Work out exactly what information needs to be stored between sessions, put it all in one object (not a gameObject, I mean something which can be serialised into a datastream of some kind) and then write all of that to a file. Look up System.IO.