User group addition and all folders appear

Hello, first of all thank you for developing software like nextcloud. But something that will benefit me and most users has been forgotten.
1- Why can’t the admin user see the files uploaded by other users?

2- A group can be added in the Users menu, but why cannot it be managed? For example, after adding a user called staff, I should be able to say that the users in this group can upload, delete files and chat.

Is there a plugin and an adjustment that includes these items? if there is no plugin, can it be done?