Had someone repair the wall of the above ground basement on the hillside, old 1950s house. They applied concrete to the wall. It has cracked and is coming off. I am going to contact him, but what I want to know what method needs to be used to repair the wall. He also did not waterproof it. Before it was a smooth finish, glossy finish, but was beginning to fade and show minute cracking. Should just have him remove the remainder and refund some money and send him away and just paint it myself? Thank you.

One doesn't "apply concrete to a wall". Maybe it was cement plaster, similar to what would be used for parging a masonry or concrete wall, The questions are (1) exactly WHAT was applied to the wall, and (2) WHY?