sharepoint online – Add the list to a permission group called MyGroup which has the permission Contribute

What I would like is to create a list where the user can only add, edit and delete records.
I have created a List and a permission group call MyGroup. I have set the permission Contribute to that group. And connect the list to the permission group. But still users can do other stuff like sort columns, group columns or even add columns. I want all this hidden. But after testing my permissions settings. The user has everything available. What am i doing wrong?
Peter