How to make separate levels

Sorry for the late reply.
CoquiGames is correct, you should use the Game Instance Blueprint, although I think (I’m not sure about this) it might also work with the Game Mode or the Game State BP but I’m not sure.
If you want info on how the Game Instance BP works, I think this video explains it

But if you want to use Game Mode and/or the game state then I will quote a EniGmaa

For a more detailed explanation you can read Rama’s reply