Prevent Users from Deleting Folders or Files

What are the files and folders? Do you mean like folders and files in the content tree? (e.g. a Folder page type and CMS.File page) If yes, it seems that they were not only deleted but destroyed - thus cannot be restored from the bin.
You have set the permissions for all content. But, check also the page type permissions and also page level permissions as they can be set differently.

Hi Juraj,

I'm talking about files and folders in the media libraries. Is there a way to prevent my staff from mistakenly deleting a folder or file on our site? Thank you.

"I tried setting it like this, but somehow I am still able to delete files and folders. Is there a way I can block folder or file deletion, even for users with 'global administrator' roles? I have many staff accounts, most of which have global roles. I can block them one by one, but that would take a lot of time."

Isn't it possible that your user account is global administrator? Check this with some dummy account assigned with given role and permissions.

Yes, my user has global administrator roles, but most of my staff also have default global admin roles. That's why I need a quick setting to block them from deleting a folder/files. I can lower their roles individually, but that takes time. Is there a way to give them permission to upload only?

Well, global administrator are not checked for any permissions anywhere! You need to change the privilege level and set it to Editor and then assign the users with roles and the roles with appropriate permissions. There is no other way.