Hi MrBraun, it looks like your shape is made up of 2 different pieces  the little sharp point does not go to the same height as the pyramid.
So that means that you will be actually building it in 2 different pieces and then combining them together at the end.
So first construct the main pyramid body, by steps like this  first draw the rectangle:
Then select it and run Construct > Offset to generate the inner shape:
Drag the inner shape upwards in z to your desired height. If you know a specific numeric height you want to have it at, type that height in and press Enter immediately before doing the drag and it will set "Distance constraint" active for the drag so that it snaps to that height:
Now select both profiles and run Construct > Loft to build the main pyramid base shape:
Now for the smaller shape you repeat the same steps but at a shorter height. Here I used Draw curve > Polygon to make a polygon balanced around the midpoint, and then turned on control points for it and dragged the right points to the side:
Now repeat the same steps as before but with a shorter height:
Now those 2 solids can be selected and combined together with Boolean union.
 Michael
