Changing from one game state to another? Explanation in thread

I have a handle of creating a turn based attack system , and a grid system to travel the level. Combing the two ? Not so much .

Here’s my question for anyone to give a starting place or tips. I want to do an old FF game style, where my avatar character is traveling the game map, and randomly gets “attack” the game goes from that top view to a turn based fully detailed attack screen with all the characters. How do you transition between those game states( not the right term I am sure) ? Its hard to explain, but its pretty common in 90s RPGs . Sorry if this is rudimentary, but I can’t really figure out the best way to do it , it feels like I’m making two games and trying to transition between them. Its probably super simple.

Sure , this could be in the blueprint forum, but I’m really asking more fundamental game design. Do I build two different systems and some how do a switch between them?