Always when game starts appears the message :“You won”. This should appear at the final if the player finishes under 120 seconds and if he makes over 120 should appear the message “game over” but it doesn’t appear.
You would want to SetTimer with 120 seconds on BeginPlay (probably on your GameMode).
The timer would only handle the GameOver event. There’s no need to do anything in between. It the player reached the end, and game isn’t over, it means he did it in time.
Player Wins if it reaches the end. No extra conditions are necessary.