How to hide shared folders from users who don't have access to it

I am trying to create two users (a,b) and two folders, (1,2)
I want user a to see and use folder 1 and user b to use 2. I dont know what I am doing wrong but user a sees folder 2 even though I have not given any permission. How can I fix this

Zitat von drinks2go

sticked at the top of this forum: Hide Shared Folders that a User can't access (workaround for access based share enum)

I did see that. It was labeled for 2.x, how do I access the mentioned file to edit it?
Do I just open with text edit and paste the source code? Sorry haven't done it before