FOSS gamedev and creative worlds

Hey, I was wondering if it is okay to take this game, remove a lot of information from it, and update it continually. The name I chose for it is "Survive", so far I got animals added, weather added, and the menus change.

Yes, but only if you also distribute the source code of your modifications, as the GPL license states.
Are you making changes to both the engine and the game or only the game?

Both.