Backup problem (data)
Can't save? Even when you click on the button to activate persistence? And so after the reboot everything disappears?
This is a technical administration problem that does not come from scripts.
To fix this permission issue, contact your technical administrator. And ask permission to write to your data folder.
The Path to find the data file : /Steam/steamapps/common/GarrysMod/garrysmod/data
You now know the source of the problem.
If you do not have an administrator who manages the technical part of your server, these links are from my own research, they are reliable and meet your needs :
Solution for Windows Server
Solution for Linux
A simple Google search with these keywords could help you: Permission + Right + File + Name of your operating system
💡 I am not the technical administrator of your server or the owner, so I don't have the power to give you the rights if you are not the administrator yourself.