Level made to saving isn't working

That could work, but you will have to re-create all that code in each level. Which is why I would recommend creating a save game function in the game instance and just feed into that function the level that you are on. You can call the function from the level BP on overlap of the trigger volume. The link I posted shows you the basic setup if you need more help figuring that part out. Should be able to modify it to your purposes.