Original Mesh takes changes from Duplicate

Hello all, I have built a wall (Cube) with the Modeling Tool, which I then copied with ALT + Drag. If I now want to halve the wall with the “Pin-Cut”, so that the lower and upper side of the wall get 2 different materials, however, is always adjusted despite display, all objects. Is this the right way to make walls and how can I unlink the elements?

If you use cube-a to make all your walls, and then edit cube-a, then all you walls will change. That’s by design.

If you want to edit only one wall, make a copy of cube-a in the content browser, drag it into the level, and edit that.