Codeman320 : when you go to a new layout with the same event sheet, not only the global variables keep their state, but the event groups stay active/inactive, as you left them at the end of the previous layout.
You can reset all of your global variables and groups manually when the condition "On layout Ends" triggers. You can use the system action "Reset global variables" if your game doesn't need most global variables to be persistent.
Generally, for variables that should reset when restarting the layout, you don't want to use global variables. Use local variables whenever you can, or store variables into a file/dedicated sprite object.