Hide Data and prevent Downloading for specific Users/Groups

Hello Community,

in my Nextcloud i hide some Files with the App custom css.
When i download the folder, where the files are saved in, these hided files are downloaded too. Of course they are, because i just hide them, and not moved or deleted.

But i wish, that some users can see and some others Users cant see this file.
And also, that some user can download hidden files, and some other user just can download the files they see in the GUI.

Is there a possibilty to to this?
Thanks much for help!

I think not. With Custom CSS you only hide them. The Nextcloud source is free software and with client side modification the user can make the files visible again. And the download is a zip file server generated (i think php) without your manipulation in CSS. But maybe you can use two different directorys for two different user groups.