Hi,
If you want an ez Stand, Crouch, Prone System which also prevents you from standing up from crouch/prone if you don’t fit in the gap - check out this little Video Tutorial
I used Pawn from Animation Starter Pack (to get the system animated) and in the video description you can find the code of the whole logic behind for the Player and in my Public G-Drive Folder you can find the project - feel free to use the content inside in any way you want!