Can't save when closing game

I am slightly more confused now.
BP_GameplayMap is my User Widget blueprint that has all the logic and variables for what appears on screen ( such as buttons, lines and what not )
BP_SaveGame is my blueprint of type “SaveGame” class. What I understood from the tutorial is that I am using this class, as place to store as variables all my other blueprints that I want saved.
By how confused I am now, I am not even sure I even know what I am talking about. I assumed that if it “saves” when switching levels ( without closing the game ), it would be a matter of I am saving it poorly to the slot ( which probably still is ), but really I have no clue where to start fixing it from.

What you said with save “BP_GameplayMap instead of SaveGame” sonunds like the next step forward, but not sure how I would go about it