In this case I would do something like this
Global Variable - Score = 0
Global Variable - HighScore = 0
Global Variable - IsRunning = 1
Global Variable - Time = 30
Everytick
IsRunning = 1 Update TextScore = 'score: ' & Score
this will update your scores
Everytick
Score > Highscore
IsRunning = 1 set global variable HighScore - Score
Set Highscore - "Highscore: " & Highscore
this will update your highscores
Every (int)1second
Is Running = 1 (-1 to Time)
this will track how much is remaining, even if the game ends early
(end of game) set IsRunning = 0
— you end your game set this to stop all the timers and scores from runnin
This will save your scores including high score.
Set text finalscore = highscore + Time(x10)
Hope this makes sense, if not I'm sure someone could offer you a more clear version.