Syntax error over here:
ShadowScoreText.text + "HighScore: " + GameScore;
You probably meant to use the equals sign instead of the plus sign after ShadowScoreText.text:
ShadowScoreText.text = "HighScore: " + GameScore;
In the future, please use code tags when posting code on the forums and include the exact error messages you get.
The error messages will contain the line numbers that the error is occurring in, and will make it much easier to debug.