So you want to cut the shape of the Sphere from the Wall, right?
In that case, you trim the Wall to the Sphere.
Model the Half sphere using the Shell Tool.
Then in 3D, select the Wall, and use the Connect>Trim Selected Elements to Roof/Shell command of the context menu. (Makes sure the Shell is not selected)
Then click the Shell to specify the element to trim the Wall to.
Then click the part of the Wall you want to keep (outside the Shell volume or inside).
Done. Also, make sure the Building Material of the Shell is stronger the the Building Material of the Wall, since the command connects the Wall and the Shell and Priority Based Connections will become effective between their Building Materials.
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