The concrete slab under the door threshold is cracked and therefore not even. When you step down on the threshold it's weak and nothing is supporting it. There's almost a half inch gap. Then the outside of the threshold overhangs the slab so there's nothing that supports the edge. What can u use to level or the concrete under threshold. And what could I do to support the edge of it outside? I submitted pics to show the problem. Thanks for your time!