3:03 PM, Wednesday July 15th 2020
Hi,
I see your intersection on the top is changing directions 3 times, but it should be a strait line. The intersections change direction only when they touch an edge.
To start an intersection, you can choose a place where an edge of cube A enters a face of cube B. Then, you can trace a line parallel to the face of cube B until it touches an edge. Then you find the face you want to continue your intersections on and continue your line parallel to that face.
Here, take a look at my form intersections and isolate to cubes to study them. They are by no way perfect but Uncomfortable said I had a good start : https://imgur.com/a/iG0n4Us
Have fun!