Hi,

I'm fairly new myself so I don't know all the solutions to this kind of problem.

What I have been doing is using one of the front/top/side views and drawing a line across the object where I want to split it into two pieces.

Then apply "boolean diff", using the line as the object to remove, and you have two pieces.

At that point you can re-create the part that is wrong or add to the existing part.

Then you use "boolean union" to put it all back together.

Frederick