Unfortunately, we do not have a French documentation yet. But if you need some support in French you can contact our friends from ILIAS France
Concerning your questions:
I understand "Stop inheritance".
That's good. Because some people do not know what this is meaning. The reason why you have to stop inheritance is, that you want to define a local permission policy only for the current folder (and not - as Jesper suggested - for all folders in courses and groups).
Does "give permission "Create files" mean I should check "file" in the list that contains "folder", "chat", etc.?
Yes! On the permission screen for the current object there are permissions (checkboxes) for "General operations", "Special operations", "Permission settings" and "Create new objects". In the last mentioned section you define which role is allowed to create which new objects in the current folder. And because you want to allow students to add new files to a folder, you have to give them the permission for this by clicking the checkbox "File" and save the setting.
I am not sure what "you have to take away all permissions for the file object" means. Does that mean that I uncheck "Read", "write", etc.?
You are right again! You do not want that users see the files of other users. So they should not have the permission "FILE IS VISIBLE" and "DOWNLOAD FILE" in the permission settings of the role MEMBER. These permissions are usually given to course and group members by default. So you have to change them. And you can do this only when you BREAK INHERITANCE before. Because otherwise the title of the MEMBER role on the permission screen is not becoming blue and a link. Now click on the link "Course member" or "Group member" to enter the permission settings of this role. These permission settings are used by ILIAS to define the permissions of new created objects in this folder (and all sub-objects too). Now, if you change the settings for "FIle", all new created files in this folder get the permissions according this definiton - which means in your scenario: Course/Group member do not see the files and cannot download them. And that's what you want and what a postbox is made for. Only Course Tutor an Course Administrator are able to download the files.
Because ILIAS is respecting ownership of objects, the user that uploads a file is always seeing this file in the folder. Ownership is overwritting the permission settings.
I hope you understand what I tried to describe.