Question PlayerSettings.resizableWindow build error

Hi,
so I tried to build my project and got this Errors:

Code (CSharp):

1. Assets\Scripts\Menu\UIManager.cs(24,9): error CS0103: The name 'PlayerSettings' does not exist in the current contex
2.  
3. Error building Player because scripts had compiler errors
4.  
5. Build completed with a result of 'Failed' in 2 seconds (1945 ms)
6. UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)
7.  
8. UnityEditor.BuildPlayerWindow+BuildMethodException: 2 errors
9.   at UnityEditor.BuildPlayerWindow+DefaultBuildMethods.BuildPlayer (UnityEditor.BuildPlayerOptions options) [0x002bf] in <bef6d2fbef1348939b77102b4cf6a6e6>:0
10.   at UnityEditor.BuildPlayerWindow.CallBuildMethods (System.Boolean askForBuildLocation, UnityEditor.BuildOptions defaultBuildOptions) [0x00080] in <bef6d2fbef1348939b77102b4cf6a6e6>:0
11. UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

So it seems like that I cannot use

PlayerSettings.resizableWindow

inside my code when I'll build the game.
My aim is it to make the first scene that appears resizable but the other scenes not. Is there any way to get the upper code working? Or just another way to get this done?

I appreciate any answer.

 

Any idea?