How do I change spawn locations when a team wins a certain amount of wins?

[Grassen]

So recently i've started to play around with math_counter entity to add to a map. What came to mind was, let's say red team wins 3 rounds the map changes spawnpoints and if blue wins a round it removes a "counter" to the score, making it so red does not progress to the next area of the map. How would I go about recreating this?
(I've attached screenshots to see what I have so far)